United testing lie-flat seats for its longest U.S. routes

United Continental Holdings is experimenting with lie-flat seats for its fleet of Boeing 737 Max 10 jets, which the airline plans to fly on its longest domestic routes.

The No. 3 U.S. carrier is working on seat designs and has completed an initial round of testing on one model, President Scott Kirby said.

Tests on a second seat are slated for this fall.

United plans to use the Max 10, the biggest version of Boeing’s upgraded 737 aircraft, to expand its luxury cabin offerings on cross-country flights beyond Los Angeles, San Francisco and Newark, N.J. The single-aisle jetliner will serve as a replacement for the carrier’s aging 757 planes in the trans-continental market, where business travelers are willing to pay a premium to stretch out.

“Trying to fly from Denver to L.A., I think you would have a hard time making the economics of lie-flat work,” Kirby said Tuesday at the International Aviation Forecast Summit in Denver. “But would Newark to Seattle work? Probably. Would San Francisco to D.C. work? Probably. We think there is demand, but it’s almost exclusively trans-con demand.”

The offerings will have plenty of competition. Some of American Airlines’ Airbus SE A321 planes offer first- and business-class cabins on cross-country routes.

Delta Air Lines has flat-bed options on its planes, while JetBlue Airways offers a premium cabin on some of its A321s.

United has 28 lie-flat seats in business class on its small fleet of 757-200s.

The planes serving the Los Angeles-Boston route will all offer lie-flat seat options in October, a company spokesman said Tuesday.

The Chicago-based carrier is scheduled to begin flying the Max 10 jets in 2020. United has orders for 100 of the largest 737 Max.