An English language article on the ITAR-TASS news website, quoting "a source at the city automatic air traffic control center," says:
“The crew of a Boeing 737-500 en route from Moscow to Rostov-on-Don did not fulfill an air traffic controller’s order and created the tense moment at 9:44 a.m. Moscow time,” he said.Another article about the near-collision, which appeared on CNN Money, gave similar information. The article on CNN Money added that the Boeing 737-500 was operated by Don-Avia and had 51 passengers and six crew on board, while the Delta plane was carrying 219 passengers and 12 crew.
The air traffic controller told the plane carrying 57 people to climb to the altitude of 2,100 meters and warned about the approaching Boeing 767-400 of the American Delta airline en route from Atlanta to Sheremetyevo,” the source said.
The American jetliner carrying 12 crewmembers and 219 passengers was descending to 2,400 meters for landing. Its crew also received instructions from the air traffic controllers.
The controller watching the Boeing 737-500 noticed that the plane continued the climb and was rapidly approaching the Delta’s jetliner. He ordered the Delta’s pilot to descent and the instruction was fulfilled promptly.
Thus, the controller prevented an air crash and the planes passed each other on the crossing courses at the distance of eleven kilometers instead of the safe 30-kilometer distance.