BOISE, Idaho (AP) — Military investigators say human error caused an Idaho Army National Guard helicopter to crash during a November training mission near the Boise airport, leading to the death of two pilots on board.

Col. Tim Marsano, a Guard spokesman, said in a statement that the pilots were practicing flying the helicopter to safety on a single working engine. To simulate loss of power, they were supposed to momentarily slip one of the engine power control levers into the lock-out position, then pull it back, decreasing power to one of the engines.

But investigators concluded one or both of the pilots pushed both control levers into the lock-out position and kept them there for too long, shutting down the engines. Marsano said they had three seconds to respond before impact, and that's not enough time to restart the engines or otherwise recover. The pilots were killed on impact.