In a country where the capitalist corporate world is supposed to be independent of government interference, or even assistance, the U.S. airliner industry has been totally reliant upon taxpayer funded NASA for developing more efficient, and safer, technologies.
NASA’s Boeing 737-130 was the workhorse of such taxpayer funded testing and developments. Serial Number SN-19437 (N515NA, tail #515) was born in 1968 (some sources say 1967), and reported for duty at NASA’s Langley Research Center in 1973. Apparently 515 was the first prototype Boeing 737 built.
I must point out that between 1938 and 1978 the U.S. airline industry was under the total regulation of the federal government, being de-regulated beginning in 1978 with the hopes that capitalist competition would reign in growing costs of operation, but in reality has created the money-grubbing passenger unfriendly monstrosity of today. Even with de-regulation the airliner industry still relies on taxpayer funded testing of new technologies.
515 took part in dozens of developments: Microwave Landing Systems, velocity vector display development, CRT electronic cockpit displays, profile descent control law development, total energy control law development, helmet mounted displays. Also, satellite-based Global Positioning System for auto-landings, ground-air data-link in lieu of voice communication, traffic flow management ATC-compatible 4-D Flight Management System development, wind shear detection research. Just to name a few.
In 1985, 515 joined several other NASA and FAA aircraft in the U.S. state of Maine, as well as in Canada, to study Runway Friction in bad weather.
In 1989, 515 got a new paint-job.
According to NASA, 515 was constantly modified, and even had two cockpits, the second cockpit being located where the airliner’s first class passengers would sit.
1990s NASA video showing 515 is use for wind-shear research. The research was done because of the increasing number of crashes being caused by the weather phenomenon called wind-shear:
High lift wing testing, 1990s.
515 retired in 2003, and now resides at the Museum of Flight, in Seattle, Washington.
NASA: 
F-16XL LAMINAR FLOW, ONCE AGAIN NASA SAVING THE AIRLINER INDUSTRY!
