The test flight of Boeing’s Starliner capsule — which turned into a monthslong stay in space for two astronauts — was a debacle in the same league as shuttle disasters, NASA said.

The head of NASA is blasting Boeing and his own agency in response to Starliner’s botched flight that left two astronauts stuck on the International Space Station for months.

NASA's new report says problems came from three main places: not enough NASA oversight, Boeing pushing its propulsion system too far, and bias in risk assessments because NASA wanted more than one pro...