PHOENIX (AP) -- Now that some airlines are making money on checked baggage, they plan to crack down on people who try to stuff oversized bags in the overhead bins.

The airlines note the carry-on policy is a federal one not set by the industry. But they agree it's only fair to the honest, fee-paying customer to keep others from trying to sneak bulky bags onto planes.

The fees for checking bags were introduced to help cover soaring jet fuel prices.

If a passenger is stopped from boarding with an oversize carry-on, American will charge that passenger the $15 fee to check it at the gate. United hasn't decided how to handle that, but US Airways says its passengers can check those bags for free at the gate.