I know, because I built and sold this program, when I was VP Sales at GetThere (a part of Sabre). TWA would have been the first, but they didn't move that quickly (then were bought by American). America West did.
GetThere was the booking engine for American Express Travel, a number of airlines (United, America West, TWA) and hotels (Hyatt).
As online advertising - especially in the travel arena - was getting red hot, I was hired by GetThere to capitalize on these opportunities. The plan was for me to work with our current partners (above) and put ads either within the booking engine (GetThere's domain) or throughout their site.
While our plans met with some initial resistance, eventually we got Amex and America West on board, and Hyatt was about to follow. United was interested. All wanted to make a couple of extra dollars and try this out. We had about 20 advertisers.
However, in summer 2001, the decision was made to close our unit (after one year), so that GetThere -- which had just been acquired by Sabre -- could focus on what it did best... technology. By then, the online ad market started tanking.
It was a great experiment. Glad to see it didn't totally die.
Vice-President, Eastern Region - Partner Marketing
Orbitz / Cheap Tickets / Away Network