What's the form?

Film in which the crash of an Avro Lancaster bomber aircraft is thought to have resulted from unauthorised low flying, until a more thorough examination of the evidence proves otherwise.

A ground crewman fails to complete maintenance on the electrical system of an Avro Lancaster, which suffers an electrical failure and crashes while attempting to land at its home airfield, killing all onboard. The Board of Inquiry rules that the accident was due to unauthorised low flying, but an RAF officer’s more thorough examination of the evidence reveals the true cause, emphasising the importance of thorough air crash investigation procedures.