The new Boeing Starliner spacecraft has lifted off with U.S. space agency NASA astronauts on board. The Starliner, after two previous attempts, launched at 10:52 AM local time on Wednesday. The astronauts are headed to the International Space Station (ISS).

Two previous attempts to send U.S. astronauts Butch Wilmore and Sunita Williams to the ISS on the first crewed flight of the Starliner were canceled before launch. Wilmore and Williams had just entered the capsule on May 6 when ground officials noted a faulty oxygen relief valve on the Atlas V rocket’s second stage. The second scrub occurred last Saturday with just under four minutes before liftoff a failure involving the computer system that controls the countdown’s final minutes was detected.

Wilmore and Williams are to spend a day in orbit before rendezvousing and docking with the orbital outpost, where they will spend about a week testing the capsule and its subsystems.

The flight will be the final test before NASA can certify Boeing to conduct routine missions to and from the space station for the government space agency.

Boeing will become the second U.S. option for human space flight along with Elon Musk’s SpaceX Dragon capsule. SpaceX has been shuttling NASA astronauts to and from the ISS since 2020.

The Starliner program has experienced years of costly setbacks and delays.

During a 2019 uncrewed test flight, the capsule was on an incorrect trajectory due to a software error and returned without reaching the ISS.

Another launch was postponed in 2021 because of a valve problem. An uncrewed capsule reached the ISS in May 2022. But the spacecraft has experienced several problems since then, including the discovery of flammable tape in the cabin and weak parachutes.