WASHINGTON — XCOR Aerospace, a company best known for attempting to build a reusable suborbital spaceplane, has laid off a significant fraction of its workforce to focus its resources instead on development of a rocket engine.

Randy Baker, chief operating officer for XCOR, told SpaceNews May 31 that the company laid off a number of employees at its facilities in both Mojave, California, and Midland, Texas on May 27. Baker declined to state how many employees were laid off, but other reports, including comments by former employees on social media, indicated that about two dozen people lost their jobs at a company that, prior to the layoffs, had about 50 to 60 employees.

Baker said that the company was concentrating its resources to develop a liquid hydrogen engine under a contract with United Launch Alliance announced in March. That, in effect, puts development of the company’s Lynx suborbital spaceplane on hold.

“Following recent breakthroughs in the effort of developing safer, cost-effective, sustainable, reliable and instantly reusable rocket engines for XCOR’s Lynx and other launchers, XCOR Aerospace has decided to focus the majority of its resources on the final development of the revolutionary liquid oxygen and liquid hydrogen (LH2) program,” he said.

ULA is interested in the engine, designated the 8H21 by XCOR, for potential use in the Advanced Cryogenic Evolved Stage, a new upper stage it plans to develop for its Vulcan launch vehicle that would replace the Centaur currently used on the Atlas 5 and on initial versions of Vulcan. ULA is also considering the BE-3U engine developed by Blue Origin, as well as the RL10 engine from Aerojet Rocketdyne currently used on the Centaur.

“Based on the immediate engine opportunities presented to us, we decided we needed to fully focus on the LH2 program for the forthcoming period,” Jay Gibson, president and chief executive of XCOR, said in a statement. “Given that we remain a small-scale company, we are planning to place more emphasis on fine-tuning the hydrogen engine program to achieve an optimal closed loop system for cryogenic rocket engines.”

The new focus on the LH2 engine is the latest in a series of changes at XCOR, a company that had worked for more than a decade on suborbital spaceplane concepts, but appeared recently to be focusing more on engine development. Last March, Gibson became president and chief executive, succeeding company co-founder Jeff Greason, who became chief technology officer. Greason and two other co-founders left XCOR last November to start an aerospace vehicle design company.

The company also made changes to its board of directors in March, removing Greason and Stephen Fleming, an early investor in XCOR. Among the company’s new board members were Michael Gass, the former president and chief executive of ULA; and Tom Burbage, the former general manager of the F-35 program at Lockheed Martin.

Lynx is a two-seat vehicle designed to take off from a runway under rocket power and make a brief suborbital flight before gliding back to a runway landing. Work on the vehicle was running far behind the company’s earlier schedules, in part because of challenges developing the vehicle’s carbon composite structure.

Speaking at the Space Access ’16 conference in Phoenix on April 8, Doug Jones, chief test engineer and the last of the company’s co-founders still at XCOR, suggested a “money problem” was delaying work on the Lynx’s wings, the last major vehicle component yet to be delivered for a prototype known as the Mark 1. He did not elaborate on the funding issue.

Jones declined at the time to give an estimate of when Lynx Mark 1 test flights would begin. “‘Light under the gear’ all depends on how our schedule moves forward,” he said. “I just don’t know at this point because there are too many imponderables in the way. We move as fast as we can move.”

In the May 31 statement, Gibson indicated XCOR was not abandoning the Lynx. “We are convinced that this effort will ensure that XCOR is better positioned to finish the Lynx Project in a more efficient, reliable and safer manner,” he said of XCOR’s decision to focus on the engine.

The company, though, is taking other steps to deemphasize the Lynx. XCOR was originally scheduled to discuss its vehicle development plans during a June 2 panel session at the Next-Generation Suborbital Researchers Conference in Broomfield, Colorado. An version of the conference agenda available on the conference website May 31 no longer lists XCOR as participating on that panel.