Urals Airliners said the flight engineer on a Tu-134 mid-hauler bound for Yekaterinburg, 870 miles northwest of Novosibirsk, fell two meters to the ground as the plane was preparing for takeoff, with all passengers already on board.
"We still do not have a clear picture of what actually happened. Perhaps he failed to notice that the staircase had already been removed," a source at Urals Airlines said, adding that "there has never been a similar incident as far as the company's staff can remember."
He said the crewman is currently in hospital undergoing a medical examination and initial treatment.
The flight was put on hold pending the arrival of a standby crew, the source said. Some of the passengers have proceeded to their destinations on another carrier, while others are still at the Novosibirsk airport waiting for the replacement crew.