If unforeseen circumstances force you to rebook an international flight from the U.S., you may face a hefty change fee - up to $500 a ticket.

But a passenger rights group has asked the U.S. Department of Transportation to adopt a $100 fee cap, arguing that the charges are exorbitant.

The U.S. airline industry collected $2.8 billion in change fees in 2013 and is expected to report even more such revenue in 2014.

Airlines say the fees are clearly described to travelers before they book flights, says Airlines for America, a trade group.