from bicycling.com:
The Best and Worst Airlines for Cyclists Airlines generally allow a bike
case that measures no more than 62 dimensional inches (length plus width
plus height) and weighs less than 50 pounds to fly as regular checked baggage.
Beyond that, you'll pay extra. All figures quoted are for one-way travel....
THE BEST
Frontier
Weight/size limits: 99.9 pounds/109 linear inches
Cost: $50
Notes: All bicycles are transported by hand, from ticket counter to
aircraft hold.
Southwest
Weight/size limits: Any bag over 100 pounds must be shipped as cargo
Cost: $50
Notes: Without exorbitant fees, this airline has managed to turn a
profit for 36 years straight.
JetBlue
Weight/size limits: 99 pounds
Cost: $50 domestic, $80 international
Notes: Bikes are cheaper to fly than pets ($100)-but Fido earns you
frequent flyer points.
IN THE MIDDLE
US Airways
Weight/size limits: 100 pounds
Cost: $100
Notes: Liability waiver required
Continental
Weight/size limits: 70 pounds
Cost: $100
Notes: no liability for soft-side cases
THE WORST
Delta (and its subsidiary, Northwest)
Weight/size limits: 100 lb
Cost: $175 domestic, $300 international
Notes: Need a laugh while you're weeping over this surcharge? Read
the rules for checking Christmas trees.
United
Weight/size limits: 50 lb
Cost: $175 domestic and Central America, up to $250 international
Notes: Weight allowance all but rules out hard cases, which weigh 30-plus
pounds on their own
American
Weight/size limits: 70lb/115 inches
Cost: $100
Notes: You also must pay the regular checked-bag fee ($20-$30).
Pack Smart
*Don't use the bike bag as your suitcase. Some carriers assess both
oversize and overweight charges.
*Read your airline's policy carefully. United, for example, will not
take packed bikes over 50 pounds, period. They also charge extra on flights
to Japan and Brazil.
*We hesitate to say this, but with increasingly stringent dimensional
and weight restrictions, hard-shell cases are looking like a poor idea.
While their protection is superb, most weigh more than 30 pounds-empty.
That said, some carriers require liability release forms for soft-side
cases.
*Airlines don't accept liability for improperly packed items, so use
pipe insulation on frame tubes. Remove quick releases and pedals, wrap
separately, and get plastic axle guards from a bike shop. For mountain
bikes, remove brake rotors. Remove your rear derailleur hanger if possible.
Use axle blocks, especially with soft-side cases.
*CO2 cartridges are prohibited in all checked bags and carry-ons.
*Checked bag liability usually tops out at $3,300 for domestic flights.
Damage must be proved. Check your homeowner's policy to see if it covers
items damaged in travel.
*Finally, it's an urban myth that your tires will burst in the cargo
hold-there's no need to deflate them.