The board's findings confirmed that all preparatory and countdown operations for Flight 157 had gone off normally, as did the flight sequence until the separation of the solid boosters. The report identified the occurrence of a leak in the Vulcain 2 nozzle's cooling circuit during this first flight phase, followed by a critical overheating of the nozzle - which led to a loss of its integrity.

This resulted in a major imbalance in the thrust of the Vulcain 2 engine due to the nozzle's deterioration, leading to a loss of control over the launcher's trajectory. The board concluded its report stating that the most probable cause of the failure of Flight 157 was the simultaneous occurrence of two aggravating factors: The degraded thermal condition of the nozzle due to fissures in the cooling tubes, and non-exhaustive definition of the loads to which the Vulcain 2 engine is subjected during flight. The board also noted that it would be difficult to simulate these additional loads during ground tests.

Meanwhile, Ariane 4 is on schedule for a 11 February launch.