MSNBC runs down a list of nine fees charged by at least a few airlines for things you might think are standard transactions, such as booking flights over the phone, checking luggage, and seating small children on your lap. One thing in particular to keep in mind when you make a last-minute reservation:3. Cashing in frequent flier miles without sufficient advance notice
Fee: $0-100 ... Some airlines will let you book a frequent-flier seat even up to the day of travel with no fee. These include Airtran, JetBlue, Northwest and Southwest. But others (Continental, Delta, and United) charge $75 if you book without enough notice (defined as three days on Continental but an unreasonable 22 days on Delta); and American charges an insane $100 if you book six days or fewer before departure.You may not be able to avoid all of these not-so-obvious fees (checking luggage is kind of essential), but knowing they exist can help you reason out whether it's worth asking for certain accommodations next time you fly. Photo by wili_hybrid.
10 most obnoxious hidden airline fees