The era of the US$400 airline fee has arrived. For an overweight checked bag weighing 71-100 pounds, Continental Airlines is charging US$400 on most international flights, and American Airlines is charging US$450 on its Asian flights. United Airlines charges US$400 for checking bags weighing 71-99.9 pounds on flights to another continent.

Those are the most expensive fees that airlines charge fliers, a new USA TODAY survey of what 13 U.S. carriers charge for services available to coach passengers has found. The survey also found:

Fees for a first checked bag, which were nominal when airlines began them four years ago, now go up to US$43. Spirit Airlines charges US$38 for a domestic flight and US$43 for an international flight for the first bag checked in at an airport.

Fees charged for the same service vary widely. Frontier Airlines charges US$50 to change an international ticket, while Delta Air Lines and United charge five times that.

Most airlines have a charge for booking a "free" frequent-flier award ticket on the phone, and some charge fliers who do the work themselves online. US Airways has the highest "free" ticket booking fees: US$55-US$90 for a phone reservation and US$25-US$50 online.

Spirit Airlines is the only carrier charging for carry-on bags. Spirit fliers pay US$30 for notifying the airline online about a carry-on bag, US$35 when calling on the telephone and US$40 at the airport.

Some airlines have eliminated discounts for paying a fee online. Continental, Delta, United and US Airways last year offered a US$2 or US$3 savings for fliers who arranged online to check a bag, but they're no longer offering the discounts.

The survey -- which USA TODAY has done the last four years -- seeks to make the fees transparent to fliers, many of whom complain they can't determine them in advance of a flight or have difficulty comparing them between airlines.

In response to complaints, the Transportation Department imposed a rule last month that requires airlines to disclose all fees for optional services with a prominent link on their websites. They also must disclose bag-fee increases on the home page or through a link on the page.

The airlines say fees keep airfares low, help cover costs and let fliers choose the services they want. American Airlines' US$450 fee for checking bags of 71-100 pounds on Asian flights was established to cover fuel costs and to discourage passengers from checking in heavy bags, spokesman Tim Smith says. The airline doesn't allow such bags on its Europe and India flights.