Efforts to tackle the engineering problems associated with powered flight began well before the Wright brothers' famous trials at Kitty Hawk. In 1804 an English baronet, Sir George Cayley, launched modern aeronautical engineering by studying the behavior of solid surfaces in a fluid stream and flying the first successful winged aircraft of which we have any detailed record. And of course Otto Lilienthal's aerodynamic tests in the closing years of the 19th century influenced a generation of aeronautical experimenters. In the 20th century, advances in aeronautical engineering soon had us soaring in safety and comfort across all the continents and oceans.
| 1901 |
First successful flying model propelled by an internal combustion engine Samuel Pierpont Langley builds a gasoline-powered version of his tandem-winged "Aerodromes." the first successful flying model to be propelled by an internal combustion engine. As early as 1896 he launches steam-propelled models with wingspans of up to 15 feet on flights of more than half a mile. |
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| 1903 |
First sustained flight with a powered, controlled airplane Wilbur and Orville Wright of Dayton, Ohio, complete the first four sustained flights with a powered, controlled airplane at Kill Devil Hills, 4 miles south of Kitty Hawk, North Carolina. On their best flight of the day, Wilbur covers 852 feet over the ground in 59 seconds. In 1905 they introduce the Flyer, the world’s first practical airplane. |
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| 1904 |
Concept of a fixed "boundary layer" described in paper by Ludwig Prandtl German professor Ludwig Prandtl presents one of the most important papers in the history of aerodynamics, an eight-page document describing the concept of a fixed "boundary layer," the molecular layer of air on the surface of an aircraft wing. Over the next 20 years Prandtl and his graduate students pioneer theoretical aerodynamics. |
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| 1910 |
First take off from a ship
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| 1914 |
Automatic gyrostabilizer leads to first automatic pilot Lawrence Sperry demonstrates an automatic gyrostabilizer at Lake Keuka, Hammondsport, New York. A gyroscope linked to sensors keeps the craft level and traveling in a straight line without aid from the human pilot. Two years later Sperry and his inventor father, Elmer, add a steering gyroscope to the stabilizer gyro and demonstrate the first "automatic pilot." |
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| 1914-1918 |
Dramatic improvements in structures and control and propulsion systems During World War I, the requirements of higher speed, higher altitude, and greater maneuverability drive dramatic improvements in aerodynamics, structures, and control and propulsion system design. |
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| 1915 |
National Advisory Committee for Aeronautics Congress charters the National Advisory Committee for Aeronautics, a federal agency to spearhead advanced aeronautical research in the United States. |
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| 1917 |
The Junkers J4, an all-metal airplane, introduced Hugo Junkers, a German professor of mechanics introduces the Junkers J4, an all-metal airplane built largely of a relatively lightweight aluminum alloy called duralumin. |
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| 1918 |
Airmail service inaugurated The U. S. Postal Service inaugurates airmail service from Polo Grounds in Washington, D.C., on May 15. Two years later, on February 22, 1920, the first transcontinental airmail service arrives in New York from San Francisco in 33 hours and 20 minutes, nearly 3 days faster than mail delivery by train. |
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| 1919 |
U.S. Navy aviators make the first airplane crossing of the North Atlantic U.S. Navy aviators in Curtiss NC-4 flying boats, led Lt. Cdr. Albert C. Read, make the first airplane crossing of the North Atlantic, flying from Newfoundland to London with stops in the Azores and Lisbon. A few months later British Capt. John Alcock and Lt. Albert Brown make the first nonstop transatlantic flight, from Newfoundland to Ireland. |
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| 1919 |
Passenger service across the English Channel introduced Britain and France introduce passenger service across the English Channel, flying initially between London and Paris. 1919 the first nonstop transatlantic flight, from Newfoundland to Ireland. |
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| 1925-1926 |
Introduction of lightweight, air-cooled radial engines The introduction of a new generation of lightweight, air-cooled radial engines revolutionizes aeronautics, making bigger, faster planes possible. |
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| 1927 |
First nonstop solo flight across the Atlantic On May 21, Charles Lindbergh completes the first nonstop solo flight across the Atlantic, traveling 3,600 miles from New York to Paris in a Ryan monoplane named the Spirit of St. Louis. On June 29, Albert Hegenberger and Lester Maitland complete the first flight from Oakland, California, to Honolulu, Hawaii. At 2,400 miles it is the longest open-sea flight to date. |
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| 1928 |
First electromechanical flight simulator Edwin A. Link introduces the Link Trainer, the first electromechanical flight simulator. Mounted on a base that allows the cockpit to pitch, roll, and yaw, these ground-based pilot trainers have closed hoods that force a pilot to rely on instruments. The flight simulator is used for virtually all U.S. pilot training during WWII. |
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| 1933 |
Douglas introduces the 12-passenger twinengine DC-1 In that summer Douglas introduces the 12-passenger twin-engine DC-1, designed by aeronautical engineer Arthur Raymond for a contract with TWA. A key requirement is that the plane can take off, fully loaded, if one engine goes out. In September the DC-1 joins the TWA fleet, followed 2 years later by the DC-3, the first passenger airliner capable of making a profit for its operator without a postal subsidy. The DC-3’s range of nearly 1,500 miles is more than double that of the Boeing 247. As the C-47 it becomes the workhorse of WWII. |
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| 1933 |
First modern commercial airliner In February, Boeing introduces the 247, a twin-engine 10-passenger monoplane that is the first modern commercial airliner. With variable-pitch propellers, it has an economical cruising speed and excellent takeoff. Retractable landing gear reduces drag during flight. |
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| 1935 |
First transpacific mail service Pan American inaugurates the first transpacific mail service, between San Francisco and Manila, on November 22, and the first transpacific passenger service in October the following year. Four years later, in 1939, Pan Am and Britain’s Imperial Airways begin scheduled transatlantic passenger service. |
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| 1937 |
Jet engines designed Jet engines designed independently by Britain’s Frank Whittle and Germany’s Hans von Ohain make their first test runs. (Seven years earlier, Whittle, a young Royal Air Force officer, filed a patent for a gas turbine engine to power an aircraft, but the Royal Air Ministry was not interested in developing the idea at the time. Meanwhile, German doctoral student Von Ohain was developing his own design.) Two years later, on August 27, the first jet aircraft, the Heinkel HE 178, takes off, powered by von Ohain’s HE S-3 engine. |
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| 1939 |
First practical singlerotor helicopters Russian emigre Igor Sikorsky develops the VS-300 helicopter for the U.S. Army, one of the first practical singlerotor helicopters. |
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| 1939-1945 |
World War II spurs innovation A world war again spurs innovation. The British develop airplane-detecting radar just in time for the Battle of Britain. At the same time the Germans develop radiowave navigation techniques. The both sides develop airborne radar, useful for attacking aircraft at night. German engineers produce the first practical jet fighter, the twin-engine ME 262, which flies at 540 miles per hour, and the Boeing Company modifies its B-17 into the high-altitude Flying Fortress. Later it makes the 141-foot-wingspan long-range B-29 Superfortress. In Britain the Instrument Landing System (ILS) for landing in bad weather is put into use in 1944. |
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| 1947 |
Sound barrior broken U.S. Air Force pilot Captain Charles "Chuck" Yeager becomes the fastest man alive when he pilots the Bell X-1 faster than sound for the first time on October 14 over the town of Victorville, California. |
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| 1949 |
First jet-powered commercial aircraft The prototype De Havilland Comet makes its first flight on July 27. Three years later the Comet starts regular passenger service as the first jet-powered commercial aircraft, flying between London and South Africa. |
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| 1950s |
B-52 bomber Boeing makes the B-52 bomber. It has eight turbojet engines, intercontinental range, and a capacity of 500,000 pounds. |
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| 1952 |
Discovery of the area rule of aircraft design Richard Whitcomb, an engineer at Langley Memorial Aeronautical Laboratory, discovers and experimentally verifies an aircraft design concept known as the area rule. A revolutionary method of designing aircraft to reduce drag and increase speed without additional power, the area rule is incorporated into the development of almost every American supersonic aircraft. He later invents winglets, which increase the lift-to-drag ratio of transport airplanes and other vehicles. |
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| 1963 |
First small jet aircraft to enter mass production The prototype Learjet 23 makes its first flight on October 7. Powered by two GE CJ610 turbojet engines, it is 43 feet long, with a wingspan of 35.5 feet, and can carry seven passengers (including two pilots) in a fully pressurized cabin. It becomes the first small jet aircraft to enter mass production, with more than 100 sold by the end of 1965. |
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| 1969 |
Boeing 747 Boeing conducts the first flight of a wide-body, turbofan-powered commercial airliner, the 747, one of the most successful aircraft ever produced. |
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| 1976 |
Concorde SST introduced into commercial airline service The Concorde SST is introduced into commercial airline service by both Great Britain and France on January 21. It carries a hundred passengers at 55,000 feet and twice the speed of sound, making the London to New York run in 3.5 hours—half the time of subsonic carriers. But the cost per passenger-mile is high, ensuring that flights remain the privilege of the wealthy. After a Concorde accident kills everyone on board in July 2000, the planes are grounded for more than a year. Flights resume in November 2001, but with passenger revenue falling and maintenance costs rising, British Airways and Air France announce they will decommission the Concorde in October 2003. |
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| 1986 |
Voyager circumnavigates the globe (26,000 miles) nonstop in 9 days Using a carbon-composite material, aircraft designer Burt Rutan crafts Voyager for flying around the world nonstop on a single load of fuel. Voyager has two centerline engines, one fore and one aft, and weighs less than 2,000 pounds (fuel for the flight adds another 5,000 pounds). It is piloted by Jeana Yeager (no relation to test pilot Chuck Yeager) and Burt’s brother Dick Rutan, who circumnavigate the globe (26,000 miles) nonstop in 9 days. |
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| 1990s |
B-2 bomber developed Northrop Grumman develops the B-2 bomber, with a "flying wing" design. Made of composite materials rather than metal, it cannot be detected by conventional radar. At about the same time, Lockheed designs the F-117 stealth fighter, also difficult to detect by radar. |
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| 1995 |
First aircraft produced through computer-aided design and engineering Boeing debuts the twin-engine 777, the biggest two-engine jet ever to fly and the first aircraft produced through computer-aided design and engineering. Only a nose mockup was actually built before the vehicle was assembled—and the assembly was only 0.03 mm out of alignment when a wing was attached. |
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| 1996-1998 |
Joint research program to develop second-generation supersonic airliner NASA teams with American and Russian aerospace industries in a joint research program to develop a second-generation supersonic airliner for the 21st century. The centerpiece is the Tu-144LL, a first-generation Russian supersonic jetliner modified into a flying laboratory. It conducts supersonic research comparing flight data with results from wind tunnels and computer modeling. |
Bonfires and beacons showed the way for early tentative transcontinental flights in the 1920s. Now complex computerized systems of navigation and air traffic control manage skies filled with as many as 50,000 planes a day over the United States. Thanks to the airplane, much about the world has changed forever, not only its commerce and wars but also its dimensions. Now that it takes only a few hours to cross a continent or an ocean, the globe has grown small indeed. And propelling virtually every one of aviation's great leaps—from the first flight to the fastest jet—has been the solving of complex engineering problems.
The first of aviation's hurdles—getting an airplane off the ground with a human controlling it in a sustained flight—presented a number of distinct engineering problems: structural, aerodynamic, control, and propulsion. As the 19th century came to a close, researchers on both sides of the Atlantic were tinkering their way to solutions. But it was a fraternal pair of bicycle builders from Ohio who achieved the final breakthrough.
Orville and Wilbur Wright learned much from the early pioneers, including Paris-born Chicago engineer Octave Chanute. In 1894, Chanute had compiled existing information on aerodynamic experiments and suggested the next steps. The brothers also benefited from the work during the 1890s of Otto Lilienthal, a German inventor who had designed and flown several different glider models. Lilienthal, and some others, had crafted wings that were curved, or cambered, on top and flat underneath, a shape that created lift by decreasing the air pressure over the top of the wing and increasing the air pressure on the bottom of the wing. By experimenting with models in a wind tunnel, the Wrights gathered more accurate data on cambered wings than the figures they inherited from Lilienthal, and then studied such factors as wing aspect ratios and wingtip shapes.
Lilienthal and others had also added horizontal surfaces behind each wing, called elevators, that controlled the glider's pitch up and down, and Lilienthal used a vertical rudder that could turn his glider right or left. But the third axis through which a glider could rotate—rolling to either left or right—remained problematic. Most experimenters of the day thought roll was something to be avoided and worked to offset it, but Wilbur Wright, the older of the brothers, disagreed. Wilbur's experience with bicycles had taught him that a controlled roll could be a good thing. Wilbur knew that when cyclists turned to the right, they also leaned to the right, in effect "rolling" the bicycle and thereby achieving an efficient, controlled turn. Wilbur realized that creating a proper turn in a flying machine would require combining the action of the rudder and some kind of roll control. While observing the flight of turkey vultures gliding on the wind, Wilbur decided that by twisting the wings—having the left wing twist upward and the right wing twist downward, or vice versa—he would be able to control the roll. He rigged a system that linked the twisting, called wing warping, to the rudder control. This coordination of control proved key. By 1902 the Wrights were flying gliders with relative ease, and a year later, having added an engine they built themselves, Orville made that historic first powered flight—on December 17, 1903.
As happens so often in engineering, however, the first solution turned out not to be the best one. A crucial improvement soon emerged from a group of aviation enthusiasts headed by famed inventor Alexander Graham Bell. The Wrights had shared ideas with Bell's group, including a young engine builder named Glenn Curtiss, who was soon designing his own airplanes. One of the concepts was a control system that replaced wing warping with a pair of horizontal flaps called ailerons, positioned on each wing's trailing edge. Curtiss used ailerons, which made rolls and banking turns mechanically simpler; indeed, aileron control eventually became the standard. But the Wrights were furious with Curtiss, claiming patent infringement on his part. The ensuing legal battle dragged on for years, with the Wrights winning judgments but ultimately getting out of the business and leaving it open to Curtiss and others.
Then a more brutal war entered the picture, and the major powers were soon vying for control of the air. World War I's flying machines, which served at first only for reconnaissance, were soon turned into offensive weapons, shooting at each other and dropping bombs on enemy positions. The fighting in the skies was matched by a fierce competition among aviation engineers on both sides. When one side built more powerful engines, the other countered with sleeker streamlining; the development of bigger planes that could drop heavier bombs was countered by improved maneuverability to get the upper hand in dogfights. With each adjustment that worked, aviation took another step forward.
Some of the most significant developments involved the airframe itself. The standard construction of fabric stretched over a wood frame and wings externally braced with wire was notoriously vulnerable in the heat of battle. Some designers had experimented with metal sheathing, but the real breakthrough came from the desk of a German professor of mechanics named Hugo Junkers. In 1917 he introduced an all-metal airplane, the Junkers J4, that turned out to be a masterpiece of engineering. Built almost entirely of a relatively lightweight aluminum alloy called duralumin, it also featured steel armor around the fuel tanks, crew, and engine and strong, internally braced cantilevered wings. The J4 was virtually indestructible, but it came along too late in the war to have much effect on the fighting.
In the postwar years, however, Junkers and others made further advances based on the J4's features. For one thing, cantilevering made monoplanes—which produce less drag than biplanes—more practical. Using metal also led to what is known as stressed-skin construction, in which the airframe's skin itself supplies structural support, reducing weighty internal frameworking. New, lighter alloys also added to structural efficiency, and wind tunnel experiments led to more streamlined fuselages. Step by step, a more modern-looking airplane was taking shape.
At the same time, a brand-new role was emerging. As early as 1911, airplanes had been used to fly the mail, and it didn't take long for the business world to realize that airplanes could move people as well. The British introduced a cross-channel service in 1919 (as did the French about the same time), but its passengers must have wondered if flying was really worth it. They traveled two to a plane, crammed together facing each other in the converted gunner's cockpit of the De Havilland 4; the engine noise was so loud that they could communicate with each other or with the pilot only by passing notes. Clearly, aircraft designers had to start paying attention to passenger comfort.
The result was a steady accumulation of improvements, fostered by the likes of American businessman Donald Douglas, who founded his own aircraft company in California in 1920. By 1933 he had introduced an airplane of truly revolutionary appeal, the DC-1 (for Douglas Commercial). Its 12-passenger cabin included heaters and soundproofing, and the all-metal airframe was among the strongest ever built. By 1936 Douglas's engineers had produced one of the star performers in the whole history of aviation, the DC-3. This shiny, elegant workhorse incorporated just about every aviation-related engineering advance of the day, including almost completely enclosed engines to reduce drag, new types of wing flaps for better control, and variable-pitch propellers, whose angle could be altered in flight to improve efficiency and thrust. The DC-3 was roomy enough for 21 passengers and could also be configured with sleeping berths for long-distance flights. Passengers came flocking. By 1938, fully 80 percent of U.S. passengers were flying in DC-3s and a dozen foreign airlines had adopted the planes. DC-3s are still in the air today, serving in a variety of capacities, including cargo and medical relief, especially in developing countries.
Improvements in the mechanisms of control and in airframe construction continued, driven by commercial considerations and, with the advent of World War II, military demands for bigger bombers and faster and more maneuverable fighters. Aviation's next great leap forward, however, was all about power and speed. In 1929 a 21-year-old British engineer named Frank Whittle had drawn up plans for an engine based on jet propulsion, a concept introduced near the beginning of the century by a Frenchman named Rene Lorin. German engineer Hans von Ohain followed with his own design, which was the first to prove practical for flight. In August 1939 he watched as the first aircraft equipped with jet engines, the Heinkel HE 178, took off.
In 1942 Adolf Galland—director general of fighters for the Luftwaffe, veteran of the Battle of Britain, and one of Germany's top aces—flew a prototype of one of the world's first jets, the Messerschmitt ME 262. "For the first time, I was flying by jet propulsion and there was no torque, no thrashing sound of the propeller, and my jet shot through the air," he commented. "It was as though angels were pushing." As Adolf Galland and others soon realized, the angels were pushing with extraordinary speed. The ME 262 that Galland flew raced through the air at 540 miles per hour, some 200 mph faster than its nearest rivals equipped with piston-driven engines. It was the first operational jet to see combat, but came too late to affect the outcome of the war. Shortly after the war, Captain Chuck Yeager of the U.S. Air Force set the bar even higher, pushing an experimental rocket-powered plane, the X-1, past what had once seemed an unbreachable barrier: the speed of sound. This speed varies with air temperature and density but is typically upward of 650 mph. Today's high performance fighter jets can routinely fly at two to three times that rate.
The jet engine had a profound impact on commercial aviation. As late as the 1950s transatlantic flights in propeller-driven planes were still an arduous affair lasting more than 15 hours. But in the 1960s aircraft such as Boeing's classic 707, equipped with four jet engines, cut that time in half. The U.S. airline industry briefly flirted with a plane that could fly faster than sound, and the French and British achieved limited commercial success with their own supersonic bird, the Concorde, which made the run from New York to Paris in a scant three and a half hours. Increases in speed certainly pushed commercial aviation along, but the business of flying was also demanding bigger and bigger airplanes. Introduced in 1969, the world's first jumbo jet, the Boeing 747, still holds the record of carrying 547 passengers and crew.
Building such behemoths presented few major challenges to aviation engineers, but in other areas of flight the engineering innovations have continued. As longer range became more important in commercial aviation, turbojet engines were replaced by turbofan engines, which greatly improved propulsive efficiency by incorporating a many-bladed fan to provide bypass air for thrust along with the hot gases from the turbine. Engines developed in the last quarter of the 20th century further increased efficiency and also cut down on air pollution.
Computers entered the cockpit and began taking a role in every aspect of flight. So-called fly-by-wire control systems, for example, replaced weighty and complicated hydraulic and mechanical connections and actuators with electric motors and wire-borne electrical signals. The smaller, lighter electrical components made it easier to build redundant systems, a significant safety feature. Other innovations also aimed at improving safety. Special collision avoidance warning systems onboard aircraft reduce the risk of midair collisions, and Doppler weather radar on the ground warns of deadly downdrafts known as wind shear, protecting planes at the most vulnerable moments of takeoff and landing.
Another area of flying advanced alongside commercial and military aviation in the last few decades of the century. General aviation, the thousands of private planes and business aircraft flown by more than 650,000 pilots in the United States alone, actually grew to dwarf commercial flight. Of the 19,000 airports registered in the United States, fewer than 500 serve commercial craft. In 1999 general aviation pilots flew 31 million hours compared with 2.7 million for their commercial colleagues. Among the noteworthy developments in this sphere was Bill Lear's Model 23 Learjet, introduced in 1963. It brought the speed and comfort of regular passenger aircraft to business executives, flew them to more airports, and could readily adapt to their schedules instead of the other way around. General aviation is also the stomping ground of innovators such as Burt Rutan, who took full advantage of developments in composite materials (see High Performance Materials) to design the sleek Voyager, so lightweight and aerodynamic that it became the first aircraft to fly nonstop around the world without refueling.
In today's world, air travel may have lost some of the original glamour that once prompted passengers to dress their best for any flight. But the miracle of flying through the air is still there to be seen, perhaps best in the eyes of a child looking down for the first time on a field of clouds. The dream of flight, a dream turned into reality by the precise work of engineers, continues to enchant.
Kent Kresa
Chairman
Northrop Grumman Corporation
I'll never forget my excitement as I watched the maiden flight of the B-2 bomber from a hot tarmac in the desert town of Palmdale, California, in 1989. The flight was the culmination of a dream by the late aviation pioneer Jack Northrop, who had first proposed the flying-wing design more than 50 years earlier. Jack Northrop had developed flying-wing bombers, but none had been widely adopted. With the B-2, however, his dream finally came of age. Watching the bomber go through its maneuvers, I couldn't help but think that this was the future of aviation, a chevron-like structure in which every part of the aircraft contributes to lift. Moreover, the bomber employed stealth characteristics—it was fortunate that the physics of radar reflectivity fit nicely with the physics of flight.
Even more than its aeronautical design, the B-2's electronics pointed toward the future. A triumph of integrated systems and circuitry, the B-2 represented a milestone in the growing dominance of electronics in aerospace engineering. This might seem strange to people not familiar with the industry. In fact, it would have seemed strange to me when I began my career in aerospace engineering in the 1960s, when the focus was on engines and structure. At the time, jet propulsion and wide-body fuselages were in the process of changing aviation dramatically by shortening the time span of air travel and making it affordable for the general public.
But since then most advances in aviation have come about as a result of electronics and its two prodigious offspring—computers and communications. I got a glimpse of the tremendous potential of these areas while I was working at the U.S. government's Defense Advanced Research Projects Agency (DARPA) in the late 1960s and early 1970s. DARPA had developed a prototype system called the ARPANET (Advanced Research Projects Agency Network), which eventually evolved into the Internet. I can't claim to have foreseen how this new medium would blossom into one of the foundations of globalism, but even then I was struck by how a network could make individual computers substantially more useful. It occurred to me that at some future point everything would be "netting," even aircraft.
When I turned to management, "netting" became a major focus of my career. It was also the driving force in many other aerospace careers as well, so that by the end of the 20th century the industry had been reconfigured by advances in electronic systems and networks. Today, for instance, U.S. military aircraft are connected by data links to external sensors and computer processing that guide them to enemy targets. Even the munitions that aircraft launch can be redirected in midflight by networks that feed them continuous real-time information. Commercial aviation grows ever more dependent on electronic networks. With air traffic expected to double by 2015, new air traffic control systems will make greater use of satellite navigation to accommodate the increase. Similarly, air cargo transport is developing radio-based systems that can track individual freight items through every point of the supply chain.
In all of these cases the ability to integrate networked systems into the operation of aircraft is setting new standards for modern-day flight. The military can achieve a more accurate and powerful impact with fewer resources. The commercial system can offer greater transportation and logistical capacity at lower costs.
As we look forward to the next 100 years of aviation, we can expect electronics to continue leading the way in innovation. Certainly there will be additional breakthroughs in aircraft design, such as flying-wing structures developed for commercial transportation and morphing wings that change their shape in flight. But it will be mainly the flight of electrons that pushes the envelope of aerospace engineering in ways we can only dream of today.