ANCHORAGE — The pilot of an air taxi that crashed in Soldotna in 2013, killing all 10 people on board, underestimated the weight of the plane’s cargo, the National Transportation Safety Board said in a report issued Wednesday.

The probable cause of the crash was the operator’s failure to account for about 420 additional pounds of unspecified cargo, which led to loading and operating the de Havilland DHC3 Otter outside its weight and center-of-gravity limits, the report said.

“Contributing to the accident was the Federal Aviation Administration’s failure to require weight and balance documentation for this type of air taxi flight,” the report says.

The de Havilland DHC 3 Otter stalled, crashed and burned shortly after taking off from the airport in Soldotna. The report says the airplane was destroyed by both the impact and a subsequent fire.

Investigators found a video of the takeoff on a passenger’s smartphone.

An analysis of the video indicated that right after takeoff, the plane’s angle of attack increased as the plane’s speed decreased from 68 mph to 44 mph in about 8.5 seconds.

The video showed the plane appear to stall at about 11 seconds after takeoff. The plane rolled right-wing down and hit the ground several seconds later.

Besides the pilot, Walter “Willie” Rediske, also killed were two families from Greenville, South Carolina: Melet and Kimberly Antonakos and their three children, ages 11 to 16; and Chris and Stacey McManus and their two teenage children.

They died during what was to be the last leg of a 10-day vacation. The families were booked on a flight leaving Soldotna to visit a remote bear-viewing lodge in Chinitna Bay.

Attempts to reach Rediske Air weren’t immediately successful Wednesday.