US airlines have been witnessing a fall in air traffic, but airline revenue has swollen owing to extra fees for services such as canceling/rebooking flights, checking bags, assigning seats and the like.

During the first half of the current year, the US airlines pocketed $3.8 billion in extra fees as compared with $2.3 billion in the same period last year.

Speaking on the extra fees, SmarterTravel's executive editor, Anne Banas, said, "Fees are much higher this year."

Airlines started charging extra fees since September 11, 2001, in order to offset downturn in air travel.

It should be noted here that some of the US airlines are charging extra fees for even using toilet on flight.

Revenue from checking bags in April, May and June soared to $669 million, representing an increase of 276 per cent from the same period previous year.

Recently, Delta Air Lines, US Airways, Northwest and American Airlines announced a new $10 fee for most flights planned for the Sunday after Thanksgiving and on January 2 and January 3.

Nevertheless, Spokesman for Air Transport Association, David Castelveter, said airlines required more revenue sources to be cost-effective.