Watch along today as NASA's Boeing Starliner Crew Flight Test finally — most likely — blasts off to the International Space Station (ISS). NASA should start streaming its coverage at 6:30PM ET on its YouTube channel, with the official launch set for 10:34PM ET. The spacecraft will carry two astronauts, Suni Williams and Butch Wilmore.

We say "most likely" because the road to this day has not been a smooth one. It was a decade ago that NASA first chose Boeing and Space X to construct spacecraft that would fly from the United States to the ISS. Boeing received a $4.2 billion contract, while NASA gave SpaceX $2.6 billion. Yet, the latter had its first successful crewed flight in 2020 and has replicated it about a dozen times since.

Boeing's Starliner failed to reach orbit during its first uncrewed orbital test flight in 2019 due to too much fuel burning. A follow-up flight was scheduled for August 2021 but was scrapped due to a valve issue, with Boeing finally reaching the ISS in spring 2022 with an uncrewed vessel. Two plans for crewed flights came and went, amongst faults in aspects such as the parachute system. Last August, Boeing announced it should have these issues straightened out by March 2024.

It's now two months later than that initial goal and Boeing, Williams and Wilmore seem prepared for take off. "We are ready, the spacecraft's ready and the teams are ready," Wilmore told the press. NASA associate administrator Jim Free added: "The first crewed flight of a new spacecraft is an absolutely critical milestone. The lives of our crewmembers Suni Williams and Butch Wilmore are at stake — we don't take that lightly at all."

Update, May 06, 2024, 11:50 PM ET: Boeing has scrubbed the supposed first Starliner Crew Flight Test two hours after it was originally scheduled to launch. The launch control teams detected an "anomalous behavior by the pressure regulation valve in the liquid oxygen tank of the Centaur upper stage of the ULA Atlas V launch vehicle." Astronauts were already onboard and had to exit the vehicle. The company has yet to announce a new launch schedule.