We’ll have to put the new era of spaceflight on hold for just a little bit, because one of the two companies NASA was relying on to start flying astronauts from American soil next year has delayed its first flight to 2018.

Boeing, together with SpaceX, is being heavily funded by NASA (to the tune of $4.2 billion) to begin launching astronauts to the International Space Station (ISS), a capability the U.S. has been without since the Space Shuttle was retired in July 2011. This has left them relying on Russian transportation, the Soyuz spacecraft, something NASA is keen to rectify.

But while SpaceX continues to make ground – not only with its upcoming manned Dragon V2 spacecraft, but with its reusable rocket – Boeing has hit a snag with its CST-100 Starliner. “We’re working toward our first unmanned flight in 2017, followed by a manned astronaut flight in 2018," said Leanne Caret, CEO of Boeing’s Defense, Space, and Security Division, at a briefing for investors this week, reported Geekwire. In other words, they’re delaying their first manned flight.

According to SpaceNews, the new timeline will see a pad abort test of the spacecraft in October 2017, where the capsule practices launching away from a malfunctioning rocket to save the crew. An unmanned orbital test flight is scheduled for December 2017, followed by a crewed flight to the ISS in February 2018. Originally, the unmanned flight was planned for June 2017, and the manned flight in October 2017. SpaceX, meanwhile, says it is still on track for 2017.

The reasons appear to be due to a problem with the weight of the spacecraft. Namely, it’s too heavy. There also seems to be some problems attaching the capsule to the rocket that will launch it to space.

^{Boeing performed a drop-test of Starliner in February 2016. NASA/David C. Bowman}

Starliner is a capsule that will eventually be capable of taking seven astronauts into space. On these first missions, though, it will take between two and four. Starliner will launch atop an Atlas V rocket on missions to the ISS, and return to Earth using parachutes to touch down in the ocean (Dragon V2, meanwhile, may eventually perform powered landings on the ground).

For NASA, the delays will be a bit of a blow. They have invested a lot of money in these private companies ($2.6 billion in SpaceX) to take astronauts to space, and they’ll want to show the benefits of doing so – while scrapping the Space Shuttle – as soon as possible. No doubt they’ll be hoping that there are no more delays after this.