I've flown with my bike. As long as it is under the luggage requirement for weight and size, then you should be ok. American has their linear dimensions on their website, and they list wieght restrictions (under 50 lb per bag). When you do check it, the bike counts as one piece of luggage. With two luggages as your luggage limit, you will get charged if you have a third piece of luggage. But from how I read it, it's better to have the bike charge at 80 bucks than the extra luggage charge of 100 bucks.
Call ahead- then go to the website and print out the luggage requirements and bring them to the airport. I also got the name of the manager ahead of time. She said she wasn't working the day I was going to fly out, but she gave me her home number and told me to have them call if there was a hassle. And that's exactly what I did. I was fine.
Koffee