I just recently checked my bike as luggage on a flight, and the whole process was a lot less painful than I expected - especially in that it resulted in my bike arriving intact and on time. What you need is a bike box (the kind new bikes come shipped in - any bike shop should give you one for free), a pedal wrench, and some styrofoam/other cushy stuff to pack around it. Pop off the front wheel, tie everything together (to avert the risk of things being lost if security pulls the box apart), stick it in the box, and tape it up. Check around for airlines that don't charge excessive amounts for carrying a bike.

I flew Air Canada, which considers the bike a checked bag with an extra $50 fee; since I already had a checked bag I paid a total of $150 for the bike. Lufthansa, I think, charged somewhat more, but apparently doesn't require you to box or disassemble the bike at all, which surprised me greatly. If fares you're looking at are close in price, check each airline's bike policy, which may become the deciding factor.