Russia's aviation safety watchdog says the pilots of a Boeing 737 jet somehow lost their plane's speed at a low altitude, resulting in a diving crash that killed all 50 people on board.

The Interstate Aviation Committee said Tuesday the plane's engines and other systems were working fine until the moment the plane hit the ground. It said the crew had failed to make a proper landing approach on their first attempt and then began a second run.

They put the plane's engines on maximum power, raising the plane's nose up at a sharp angle, causing a quick loss of speed. The crew then tried to gain speed by taking the plane into a dive but hit the ground at a near-vertical angle in a spectacular crash.