There's no release date yet, but Qantas has shown off a prototype of a Windows Phone 7 check-in app at the Mix 11 conference in Las Vegas. As well as allowing you to check-in, the app promises to "use location software to provide predicted journey times". That sounds intriguing, but it leads to two obvious questions.
The first is how this would work when you're in the air and the app needs to run in flight mode. That said, the second of the two screenshots includes a "leave for airport" message, so perhaps the emphasis is on getting to the airport on time rather than what happens in the air.
The second and bigger question is: why develop for Windows Phone 7 when there's still no sign of an Android or BlackBerry app? I'm a fan of the Windows Phone 7 look and I'm all for diversifying from the idea that mobile apps simply means iOS, but you'd have to think building something for Android would help a lot more frequent flyers.