Blue Origin engineer Gary Lai will replace "Saturday Night Live" comic Pete Davidson in the space tourism company's latest flight, it said on Monday.
Davidson had pulled out after the flight, originally meant to launch this week, was postponed to March 29 to run some more pre-flight tests on one of the vehicle's subsystems.
The company, in a brief notice first posted on Twitter, gave no immediate explanation for the change or Davidson's withdrawal from the manifest of Blue Origin's fourth commercial flight since last summer.
Davidson, 28, the boyfriend of reality TV star and socialite Kim Kardashian, had just been officially named as Blue Origin's "honorary guest" to join five paying customers on the flight initially set for March 23.
The suborbital joyride, lasting about 10 minutes from lift-off to touchdown, will ascend to about 350 000 feet (106km), treating passengers to a few moments of weightlessness before a descent back to Earth for a parachute landing.
Lai joined Blue Origin in 2004 and is the chief architect of the New Shepard spacecraft, a reusable rocket system that can take astronauts and research payloads to space.
The other passengers include angel investor Marty Allen, real estate veteran Marc Hagle and his wife Sharon Hagle, University of North Carolina professor Jim Kitchen and George Nield, founder-president of Commercial Space Technologies.