A Delta airlines worker is seen as luggage is loaded onto the plane at the Fort Lauderdale-Hollywood International Airport in Fort Lauderdale, Florida.

The airline, among others, is taking basic economy abroad , in hopes that it will drum up more revenue as record numbers of passengers are traveling by air. Airline executives, including those at Delta, estimate that about half of passengers opt to pay for a higher coach-class fare than selecting the cheaper basic economy.

Starting in April, Delta Air Lines will charge passengers who book highly restrictive basic economy fares $60 each way to check a bag for travel between the U.S. or Canada and Europe or North Africa.

U.S. airlines collected nearly $4.2 billion in checked baggage fees last year. That sum could rise even more as airlines bring such fees international.

The fee to check the bag — $60 each way — is the same sum that Delta is offering travelers to "upgrade" to regular economy, which offers a free checked bag. When travelers book on Delta's website, a screen pops up with a column of almost all of X's next to the mostly once-free perks that basic economy travelers won't receive, such as selecting their own seats. A second checked bag will cost basic economy passengers $100 each way.

The change starts April 10, 2018. The new policy is similar to what the crop of low-cost trans-Atlantic carriers are charging travelers.

American Airlines is also bringing basic economy tickets international and passengers opting for those fares may need to pack even lighter. The fares are available on some trips to Mexican cities, including Cancun, but passengers on those tickets aren't allowed to use overhead bins to store their carry-on bags.

The Department of Transportation recently dropped a proposal to force airlines to disclose baggage fees at the start of the ticket purchase.

Airlines meanwhile, are fighting airports from raising fees of their own on passengers. The nation's airports are pushing lawmakers to increase the cap on the so-called passenger facility fee, which is aimed at improving airports, by $4 to a maximum of $8.50 per flight.