NASA and Boeing announced that Starliner will not carry astronauts until 2028, targeting an uncrewed test flight for December or January. The delay follows severe propulsion failures during the Crew Flight Test in 2024 that stranded two astronauts on the space station for months.
Technical Failures and the Road to Grounding Starliner
Boeing’s Starliner capsule has faced a difficult path toward routine crew transportation. The vehicle first flew uncrewed in December 2019 on Orbital Flight Test, failing to reach the space station after suffering problems with its onboard timing system. A second uncrewed flight in May 2022 reached the station despite the failure of two orbital maneuvering and attitude control thrusters.
The challenges intensified during the Crew Flight Test launched in June 2024, which carried NASA astronauts Suni Williams and Butch Wilmore for what was supposed to be a 10-day stay. Shortly after separation, the spacecraft encountered helium leaks and the failure of five of Starliner’s 28 reaction control system thrusters. Although the capsule successfully docked with the orbiting laboratory, an independent review board later classified the propulsion mishaps as a close call that put the crew in jeopardy.
NASA ultimately decided against risking a crewed return on the vehicle. Starliner landed uncrewed in September 2024, while Williams and Wilmore remained on the station for an extra six months before returning home aboard a SpaceX Crew Dragon capsule in March 2025. In February, the agency formally declared the flight a Type A mishap, representing the most serious classification.
Valve Degradation and Thruster Corrosion Fixes
Joint NASA and Boeing investigation teams traced the root causes of the 2024 flight anomalies to specific chemical and thermal vulnerabilities. The helium leaks were linked to valve degradation caused by exposure to nitrogen tetroxide, the oxidizer used in the propulsion system.
“That is why the material of the seal was changed. We also realized we needed to select seals that were on the larger side of the tolerance spectrum. Boeing has implemented all of those changes on the Starliner-1 spacecraft already.”
Engineers also determined that corrosion caused the crew module thruster anomaly. Agency officials explained that residual hydrazine propellant combined with carbon dioxide from the atmosphere to create the corrosive buildup. To prevent this, Boeing established procedures to flush out the hydrazine and maintain a continuous purge isolating the thrusters from the environment. The company is replacing valves across all 12 crew module maneuvering thrusters and redesigning service module poppets.
Starliner-1 Test Flight and the Timeline to 2028 Crewed Missions
The next major milestone for the program is an uncrewed Starliner-1 mission scheduled to fly in December of this year or January 2027. This flight will serve as an engineering evaluation to test improved thermal environments and validate valve upgrades. However, because some major structural modifications cannot be fully tested until after that flight, a significant operational gap remains before the next launch.
Following the uncrewed test, NASA and Boeing will complete service module thruster valve design modifications and install new crew module thrusters, upgraded batteries, and parachute adjustments. Current agency planning targets a return of astronauts on Starliner-2 by 2028. Veteran agency astronaut Warren “Woody” Hoburg will command the Starliner-2 mission.
Commercial Crew Strategy and Future Destination Plans
NASA administrators continue to emphasize that a dual-provider model remains vital for the agency’s long-term operations. While SpaceX currently serves as the sole operational U.S. commercial crew transporter through its Falcon 9 rockets and Crew Dragon capsules, officials stress that maintaining two independent systems is essential for ongoing access to low Earth orbit.
Certifying Boeing’s spacecraft supports the planned retirement of the International Space Station in 2030 and prepares the agency for future commercial space stations once SpaceX hardware phases out. In addition to vehicle modifications, NASA intends to exercise options for a fifth and sixth Starliner flight and will work with Boeing and United Launch Alliance to certify the Vulcan rocket for crew transportation after the Atlas V rocket completes its final flight.
