Airbus SE said that one of its most ambitious projects for future propulsion — using hydrogen to power an aircraft — is progressing slower than planned because of the technological hurdles involved, dealing a setback to the industry’s efforts to clean up air travel.

Airbus delays plans to fly a hydrogen-powered commercial aircraft by 2035, citing slower than expected advances in technology.

Airbus acknowledged on Friday that progress on developing an aeroplane operating on hydrogen was slower than expected, but said it was not reviewing its approach to decarbonising aviation.