The ultimate race between SpaceX’s Dragon 2 and Boeing’s Starliner.

Back in 2014, SpaceX and Boeing both received contracts under NASA’s Commercial Crew Development program to build spacecraft that could carry astronauts to the International Space Station. The program is intended to allow NASA to launch astronauts on American spacecraft again, something that hasn’t happened since the last flight of the Space Shuttle in 2011.

The spacecraft being developed by SpaceX and Boeing—the Dragon 2 and the CST-100 Starliner, respectively—proved to be more difficult than originally anticipated. Both companies pushed back their plans for 2017 flights to 2018. Elon Musk recently said the Crew Dragon, which is what NASA calls the Dragon 2, is “way more difficult” than the cargo version of the spacecraft that is used to take supplies to the ISS. “As soon as people enter the picture, it’s really a giant step up in making sure things go right,” said Musk at a recent panel on the commercial crew program. “The oversight from NASA is much tougher.”

However, the work to achieve flights next year seems to be progressing nicely. NASA along with Boeing and SpaceX have indicated that they are on track to hit target launch dates in 2018.

SpaceX plans to launch its Dragon 2 on an upgraded version of the Falcon 9 rocket known as Block 5, currently in development. The Block 5 iteration of the Falcon 9 should produce more thrust in all engines and have reinforced landing legs. Boeing plans to launch the Starliner on an Atlas V rocket supplied by United Launch Alliance (ULA), a joint venture between Boeing and Lockheed Martin.