WASHINGTON — Three of the co-founders of suborbital spaceplane developer XCOR Aerospace, including the company’s former chief executive, are leaving the company for other pursuits, the company announced Nov. 23.

XCOR Aerospace said in a statement that Jeff Greason and Dan DeLong, the chief technology officer and chief engineer of the company, respectively, were “stepping back” from those positions “to turn their attention to pursue other interests.” A third co-founder, Aleta Jackson, was not mentioned in the release but is also leaving the company.

“Both Jeff and Dan are true pioneers in our business. It’s their vision and their perseverance that helped us getting to where we stand now,” Jay Gibson, chief executive of XCOR Aerospace, said in a statement. “Lynx is now in the good hands of XCOR’s highly capable and talented technical, engineering and program teams.”

Greason, DeLong, Jackson and Doug Jones founded XCOR in Mojave, California, in 1999 after being laid off from Rotary Rocket Company, a company that was developing a reusable launch vehicle. XCOR initially focused on developing rocket engines, but later expanded its efforts to include a suborbital spaceplane that evolved into the Lynx design now under development by the company.

Greason served as chief executive of XCOR for most of the company’s existence, but moved into the chief technology officer position in March when the company hired Gibson. Greason will retain his position on the company’s board of directors.

Work on Lynx, a two-seat vehicle designed to take off from a runway under its own rocket power, has progressed slowly over the last few years. Recently, though, the company has released images of sections of the prototype “Mark 1” Lynx being assembled and tested in Mojave.

“2016 will be an exciting year in which we’re about to reach some truly significant milestones,” Gibson said in the statement. “Over 350 clients are as eager as we are to undertake the first trip into space.”

XCOR, however, has not released a schedule for beginning Lynx test flights, a practice that dates back to Greason’s time as chief executive. The company reiterated that approach in an October newsletter.

“The fact is that we are in a process in which you just can’t rush things,” said Harry van Hulten, director of flight test operations for XCOR. “For the first time in history we are developing a genuinely instantly reusable launch vehicle and there’s no building instructions, best practices or timeline available for something so ground breaking.”