With online travel sites battling with some airlines, where does that leave travelers shopping for flights online? The simple answer is that they’re going to have to do more digging.

American Airlines removed its flight listings from Orbitz.com last month, when the companies could not agree on a new contract, and Delta withdrew its fares from CheapoAir.com, OneTravel.com and Bookit.com. More recently, Expedia.com dropped American flight listings. Delta has also notified Airfare.com, CheapAir.com, Vegas.com, AirGorilla.com and Globester.com that it will no longer allow its fares to be included on their Web sites in the United States and Canada after Friday.

The moves represent a standoff over the fees that airlines must pay to list their flights with online travel agencies. And at least one major fare distributor, Sabre, which runs a computer system that allows travel agents to see flight and fare information, joined the fray on Wednesday, announcing that it would end its distribution deal with American in August  a month before the end of its contract  and, in the meantime, would make American fares harder to see in its displays.