Delta Air Lines Inc. is hanging on to one of the Boeing 747 jumbo jets it retired last year, a reprieve for an aircraft increasingly out of favor in the industry.

Four of the 16 humpbacked wide-bodies were pulled from service in 2014 as Delta moves toward retiring the entire fleet by 2017. One of these four planes will be retained as an operational spare and may be used for charter flights and when another plane has mechanical problems, said Michael Thomas, a spokesman.

A memo distributed to Delta pilots Jan. 6 says the four- engine jumbo would be flown between Atlanta and Honolulu between late May and mid-August. A twin-engine Airbus Group NV A330 now serves that route. Thomas said he couldn’t confirm the details in the memo, saying only that the 747 could be deployed for various purposes.

Like other airlines, Delta has been retiring its jumbos in favor of smaller, more fuel-efficient jets that can make flights once reserved just for the largest planes. About 17 percent of the global fleet of 747-400s, the version operated by Delta, was in storage last month, according to data compiled by Bloomberg.

Delta’s 747s averaged 22.4 years of age as of the carrier’s third-quarter regulatory filing, the second-oldest aircraft type among its 764 jets. Delta and United Airlines are the only major U.S. airlines flying the 747 in passenger service, and United also plans to retire its jumbos.

Boeing Co. has struggled to sell the jet’s latest model, the 747-8, failing to pick up any net new orders last year and has cut back on monthly production.

More Pilots

For Delta, the 747’s retention also means it will have to keep more mainline pilots, rather than shifting them to other aircraft, since it will have 13 of the jumbos this year instead of 12, the memo says. The carrier said in September it will let as many as 50 pilots retire early as it pulls the jumbo jets from its fleet.

Kelly Regus, a spokeswoman for the Delta chapter of the Air Line Pilots Association, said pilots shouldn’t suffer from the airline’s retirement of its 747s. The airline’s recent decision to buy 50 wide-body aircraft from Airbus means it will have more long-haul jets in the next few years, even with the 747’s phase- out.

“This is Delta’s decision not ours, but we see a bright future with a profitable airline,” Regus said.

This article was written by Michael Sasso from Bloomberg and was legally licensed through the NewsCred publisher network.