On this day in economic and financial history...

Two of the most important "first flights" in aviation history have taken place on Dec. 17. On Dec. 17, 1903, Orville and Wilbur Wright made the first successful powered heavier-than-air human flight in history. And on the 32nd anniversary of that historic flight, the revolutionary Douglas DC-3 took off into the history books.

The legend of Kitty Hawk
The Wrights had been interested in flight for years before their first successful effort. Early efforts at flight, particularly three notable attempts in 1896, sparked the brothers' interest, and they began work on aeronautics experiments in 1899. Their great breakthrough -- which was so essential to powered fixed-wing flight that it remains a standard to this day -- was to devise three-axis flight controls. Earlier builders had believed that flight was little more than elevated locomotion, ignoring the possibility of side-to-side tilting movements (or "roll," in flight dynamics) in their designs.

In 1900, the Wrights began experiments with gliders at Kitty Hawk, N.C., and continued experiments until 1902. In 1903, the brothers built the Wright Flyer 1, their first powered aircraft, with a 12-horsepower engine and a maximum speed of 30 miles per hour. On Dec. 14, they attempted a flight, but a minor mistake botched the effort and damaged the aircraft. After repairs, the Wrights tried again on Dec. 17, making four brief but successful low-altitude flights, with the final attempt remaining aloft for a minute and traveling 852 feet.

The Wrights gained a patent for their methods in 1906, and they vigorously defended it. Their obsessive (but not unjustified) protection of this patent, and later patents, held back the development of an American aircraft industry for years until government pressure led to the establishment of an aircraft industry cross-licensing organization, or patent pool, during World War I.

By 1916 the Wright's aircraft company had merged with a competitor, but the new entity changed its name to Wright Aeronautical in 1919. This company gained enough importance to join the Dow Jones Industrial Average (^DJI 0.69%) in 1928, becoming the first aviation-focused company in the index's history. A year later, it merged again to become Curtiss-Wright (CW 0.94%), which grew into America's largest aircraft-manufacturer by the end of World War II. That company is much smaller today, as it operates only as a specialist manufacturer of various advanced industrial components.

Only three other aviation companies have ever been members of this exclusive index: Boeing (BA -0.76%); United Technologies (RTX -0.18%), which first joined as United Aircraft in 1939; and the United Aircraft and Transport Corporation, which was a Boeing-led aviation trust that was broken in 1934 and was a direct predecessor to United Technologies.

Success takes flight
The Douglas DC-3 was one of the most successful aircraft ever flown. Its legacy began on Dec. 17, 1935 with its first flight, which was scheduled as a tribute to its progenitor. It "made air travel popular and airline profits possible," according to Boeing. Its comfort and reliability, combined with its superior economics, led to its utter dominance of the air. Within four years of its first flight, more than 90% of the nation's airline passengers flew on either DC-3s or their immediate predecessors, the DC-2s.

More than 10,500 DC-3s were built by 1944, of which more than 10,000 were military variants for World War II. Another 8,000 were produced by licensed manufacturers. The DC-3 shortened transcontinental flights to between 15 and 17 hours, eliminating the earlier transcontinental travel method of combined short-hop flights and overnight trains. It was so well-built and functional that an estimated 2,000 are still flying to this day, primarily in developing nations, where it is prized for its ability to land on unpaved surfaces.

Douglas Aircraft, the DC-3's manufacturer, merged with McDonnell Aircraft to form McDonnell-Douglas in 1967. Four decades later, McDonnell-Douglas merged with Boeing, whose 247s had been pushed out of prominence decades many years earlier by the DC-3.

Boeing was there for the early days of aviation, and it's now one of two major aircraft manufacturers leading the industry into the future. But that barely scratches the surface of Boeing's business model and opportunities. The Motley Fool's premium research service has a wealth of information on Boeing's fundamentals, strengths, weaknesses, opportunities, and threats to help you better understand whether its stock is really worth your money. Click here to subscribe today.

It's time to clean up this place
The Clean Air Act was signed into law by President Lyndon Johnson on Dec. 17, 1963. It established a framework for government antipollution controls that would later be greatly expanded in subsequent extensions and amendments in 1970, 1977, and 1990. These legislative acts led to the formation of the Environmental Protection Agency, as well as numerous controls and quality standards for a wide range of polluting activities, from motor vehicles to manufacturing plants.

The standards adopted by the 1990 amendment have been estimated to confer a $12 trillion economic benefit (with high and low estimates ranging from $1.4 trillion to $35 trillion) to the nation for the period of 1990 through 2020. As a result of the Clean Air Act's provisions, in 2010, 240,000 fewer Americans were estimated to have died, and huge reductions of health incidents added 17 million more workdays to the nation's economy. By 2020, a cumulative 22 million life-years (the aggregate increase in life expectancy across all Americans) are expected to be gained as a result of the health benefits conferred by the Clean Air Act's pollution controls.

A dynasty built on "d'oh"
One of the most iconic TV shows in American history began on Dec. 17, 1989, when Fox, a division of News Corp. (FOX), broadcast the first full-length episode of The Simpsons. The Simpson family had already been around for years as an animated interude on The Tracy Ullman Show, but its half-hour premiere episode, "Simpsons Roasting on an Open Fire," finally gave Homer, Marge, Bart, Lisa, and Maggie a platform for worldwide domination.

The Simpsons has since gone on to become the longest-running scripted primetime television series in American history, and it has produced more than 500 episodes over 24 seasons to date. The program and its ever-expanding cast of characters have generated billions of dollars in revenue for News Corp, with Statistic Brain calculating the total Simpsons take to date at more than $12 billion. That's likely to be an understatement, as $750 million worth of Simpsons merchandise was sold in 2008 alone.