SpaceX will reportedly no longer be sending a pair of space tourists to circle the moon this year.
The reason for the delay is unclear.
The flight was announced in February 2017, with SpaceX saying that two unidentified private citizens had put down a "significant deposit" for the trip and that other flight teams had expressed interest in taking a similar journey.
The plan was for the tourists to fly on a Dragon Crew spacecraft launched from Earth by a Falcon Heavy rocket.
SpaceX did not immediately respond to a request for comment.
On Friday, Musk challenged Boeing's assertion that it would put the first human on Mars before SpaceX does.