Quick answer..

The FAA prohibts smoking on any US commercial carrier entering or leaving the US.

Since this has nothing to with miles or points, i'm going to move it over to TravelBuzz.

Edited to add:

Smoking is banned by statute on almost all U.S. domestic flights, and is prohibited by international agreement on nonstop flights operated by Australian, Canadian, New Zealand and U.S. carriers between their territories. The vast majority of smoking bans on international flights serving the United States are the result of voluntary action by airlines, with encouragement by the U. S. Government.

http://ash.org/nosmokair.html

Flipside

[This message has been edited by flipside (edited 08-13-2003).]