We asked American Airlines to offer a statement. Here it is:
Kayak/Sidestep has advised American Airlines that they will no longer display our content.
We are disappointed and hopeful that this issue can be resolved in the near future so that American Airlines will again display on the Kayak/Sidestep sites.
Our schedules and fares remain available through many other Meta-Search Engines such as Mobissimo and Farecast for purchase through our award-winning website, AA.com. Tickets already purchased remain valid for customers traveling on American.
UPDATE July 24, 9am ET:
I couldn't help noticing that Steve Hafner, the CEO of Kayak, posted a comment on the TechCrunch blog offering his version:
Translated: American asked us to suppress search results from competing websites as a condition to displaying their fares. This is simply not something that Kayak will do. Imagine Sony telling Best Buy that they couldn’t sell Panasonic?
Here's Kayak's official statement:
At Kayak.com, we are dedicated to providing a comprehensive and objective display to our users. We’re unwilling to amend this pro-consumer philosophy that is the core of our business by suppressing results based on a partner’s request. We welcome American Airlines to rejoin Kayak.com’s objective results at any time.
UPDATE July 28. For the nitty gritty on this topic, see The Cranky Flier's recent post.