A National Airlines B747-400 freighter that crashed seconds after takeoff from Bagram, Afghanistan, in April 2013, was likely caused by inadequate restraint of large military vehicles being carried onboard which broke loose and went through a bulkhead disabling two hydraulic systems and making the aircraft uncontrollable, according to a National Transportation Safety Board (NTSB) investigation. The crash killed seven crew members at the start of the flight to Dubai.

The aircraft was carrying carried 207 tonnes of cargo, including five mine-resistant ambush-protected (MRAP) vehicles, weighing between 12 and 18 tonnes each, which was being handled on behalf of US Transportation Command.

The NTSB report said that upon takeoff, “the airplane immediately climbed steeply then descended in a manner consistent with an aerodynamic stall.” The resulting investigation, “found strong evidence that at least one of the MRAP vehicles . . . moved aft into the tail section of the airplane, damaging hydraulic systems and horizontal stabilizer components such that it was impossible for the flight crew to regain pitch control of the airplane.”

The report added that the FAA’s “inadequate oversight of National Airlines’ handling of special cargo loads, such as that being carried on the accident flight,” contributed to the accident. The investigation found that National Airlines’ cargo operations manual not only omitted critical information from Boeing and from the cargo handling system manufacturer about properly securing cargo, but it also contained incorrect restraining methods for special cargo loads.

The NTSB recommended the FAA create a certification process for personnel responsible for the loading, restraint, and documentation of special cargo loads on transport-category aircraft. Other recommendations call on the FAA to improve its ability to inspect cargo aircraft operations, specifically those involving special cargo loads.