Note: The information in this article is time-sensitive and subject to change. Always check with airlines ahead of time.
BIKES ARE BIG. And so when you fly with your bicycle, that one geometric fact means that airline companies are likely going to charge you extra.
How much extra depends on the airline. Fees range from JetBlue's and Southwest's reasonable $50 per bike each way to the $200 one-way fare US Airways and Delta charge. At $400 in added fees, a round-trip on Delta between Atlanta and Los Angeles would be cheaper if your bike flew as a passenger.
Some airlines are getting the memo. Beginning April 13, Frontier Airlines ended its bike-handling fee for passengers of the more expensive "Classic" and "Classic Plus" tickets. And for the past two years, in honor of the Tour de France, JetBlue has made bike transit free from July 1 to July 30 (an airline spokeswoman could not confirm that the promotion would happen again this summer).
A portion of the bike fee is based in reality. Larger bags are harder to load and require special handling by the ground crew. In rare circumstances—as with visible damage to a hard-shell case, or divine intervention—airlines may even pay for damages.
The majority of airlines will, theoretically, waive the bike fees if your bicycle doesn't exceed size and weight restrictions of a "normal" bag, but unless you're riding a collapsible, BMX, or kid's bike, that's a long shot. The "normal" size and weight of non-oversize baggage most airlines seemed to have settled on is 62 dimensional inches (the sum of the length, width, and height) and lighter than 50 pounds.
First things first. Before your bike flies, it'll need to be in box form. Airlines typically prefer hard-shell cases or cardboard bike boxes, but soft cases can work provided there is ample padding. You'll have to remove your pedals and secure your handlebars (or you can encase both in foam or packing material).
If you're flying business class or internationally, the airline may waive some of the baggage fees. It'd be wise to check ahead with your airline if a leg of your journey involves a small regional aircraft, which may not have space for your oversize bag.
• $150 for each bike bag.
American Airlines 
• $150 charge for each bike.
Delta Airlines 
Frontier Airlines 
• $50 each way; the bike also will count as your one free checked bag.
• Free if less than 62 dimensional inches and under 50 pounds but will take the place of a free checked piece of luggage.
Southwest Airlines 
• $100 each way.
United Airlines 
• $200 each way.
US Airways 
• $25 if less than 62 inches in total dimension and it's your first bag.
Get a pro bike racer's take: "Setting Myself Free, or How to Fly With a Bike "