Boeing Co. and NASA pushed back by four days the return home of two astronauts from the International Space Station, the latest disruption for a program that has been beset by delays.

The mission using Boeing’s CST-100 Starliner capsule will now happen on June 26, instead of the previously scheduled June 22 target, NASA told a press briefing on Tuesday.

Boeing’s space taxi docked with the orbiting laboratory on June 6 as part of a critical flight test for NASA. Initially, the crew was supposed to stay on board the station for about a week.