Here and here are sites that list a timeline of when smoking was restricted in many locations in the US.

Summary:
1973 - airlines must create non-smoking sections.
1979 - Cigars and pipes banned on planes.
1987 - banned on flights under 2 hours.
1990 - banned on interstate busses and flights under 6 hours (effectively all continental US.
2000 - banned on international flights to/from the US.

I know some (maybe all) of the US airlines banned smoking before the 2000 regulation took effect.