The game of chicken between AMR Corp.’s (NYSE:AMR) American Airlines and online travel sites Orbitz (NYSE:OWW) and Expedia (Nasdaq:EXPE) has claimed its biggest casualties to date: a big slide in the ticketing sites’ profit and share prices.

American and the booking companies have been feuding over what travelers probably view as a technicality: whether the sites can use their own platforms or whether they must use American’s proprietary ticketing system.

While the fight is far from over, the airline clearly has won the first round: both online travel sites have taken big hits in both income and share price this month. Orbitz shares last Wednesday slid 8% after the release of disappointing fourth quarter earnings.  The company’s loss widened to $78 million from $18.5 million a year earlier.

Orbitz shares have slid 35% since American yanked its fares off the site on Dec. 21.

Earlier this month, Expedia said fourth-quarter earnings dropped some 30%  — even though the company’s sales (on increased hotel bookings) rose by 14%.  Shares skidded down 17% on the news, and the stock is down roughly 30% from its 52-week high.

American may appear to be drawing a line in the sand over a technicality, but that fine point is worth big bucks. At issue is whether the online travel sites — including Travelocity, a division of former AMR subsidiary Sabre Holdings — can continue to use their own global distribution systems or whether they must use American’s proprietary ticketing technology when booking its flights.  American’s own system is more cost efficient for the airline and it reinforces the brand with its customers. The online booking sites make less money by going through the American system and say that approach limits transparency and choice.

Participating U.S. airlines pay online travel sites about $1 billion a year in fees for the use of their ticketing platforms (Southwest Airlines (NYSE:LUV) always has made online fares available only through its own website).  The war of words with Orbitz turned to action on Dec. 21, when American pulled its ticket listings from the site.  When Expedia responded by “hiding” American fares on its site the next day, the airline also yanked its fares from that company.

But not every online travel firm is holding the line against American’s demands. Priceline.com (NASDAQ:PCLN) cut a deal with American to make the airline’s flights available on its site – a development that could place the other sites at a competitive disadvantage.  Priceline shares are up 152% over their 52-week low last July.

Bottom line: In the standoff between American Airlines and online travel sites, the latter’s earnings slides and stock-price hits are a pretty big blink – particularly as companies like Priceline have shown their willingness to deal.  Orbitz CEO Barney Harford basically admitted as much in a conference call with analysts last week by saying despite shifting nearly half of its ticket volume to other airlines “we are still feeling some impact”.  And the company is looking at a first quarter coming in below analysts’ expectations as well. 

The challenge will only multiply if other airlines take cues from American and deliver their own ultimatums to the online ticketing sites — a tactic that makes sense as all airlines look for ways to cut operating costs and boost revenue. In December, Delta Air Lines (NYSE:DAL) cut ticketing ties with three small sites: cheapoair.com, bookit.com and onetravel.com.  In the end, cutting the right deal with airlines might be the best way for online travel sites to keep flights posted — and profits and share prices rising.