"American, and the airlines in general, are trying to get more control and reduce costs for their distribution," said Ray Neidl, an airline specialist with the Maxim Group.
The removal of major airlines from such travel sites would not necessarily mean higher airfares, but makes those super-cheap tickets harder for passengers to find.
"It's going to mean extra work because you are going to have to look at AA.com and also your favorite online travel agency," Hobica said. If American and other airlines pull out of other travel sites, "it will kind of be back to the old days when you got on the phone and called American and called United.
"I don't see that happening," Hobica said.
Customers might also find it harder to save money with multi-carrier itineraries. For instance, a one-way ticket from Chicago to San Francisco on American paired with a one-way ticket back on United might be cheaper than a roundtrip ticket on either airline.
"The multi-carrier itineraries disappear in a puff of blue smoke," Wallace said. "Those multi-carrier initiatives are often the cheapest prices."