The pilot of the cargo Boeing 737 that almost crashed into an Airbus with 136 passengers on May 29 was the one responsible for the planes coming so close that the blips on the radar merged (Metro grab on right), an inquiry has revealed.

“The pilot of the cargo flight is prima facie responsible for the near-mishap (60 nautical miles from the city airport). The probe has revealed that he was not adhering to the flying altitude assigned by Dhaka ATC (air traffic control),” a senior airport official, who was in the inquiry team, said on Sunday.

“The pilot accepted that he had descended more than the assigned level, but claimed he was asked to do so by the ATC,” the official said.

The recorded conversation between the watch shift officer of Calcutta ATC and his Dhaka counterpart nailed the lie.

On noticing that the Alliance Air cargo plane had descended below 18,000 feet, the level assigned to it, the watch shift officer of Calcutta ATC had immediately contacted Dhaka for a clarification.

“Have you assigned him a level below 18,000 feet?” he asked his Dhaka counterpart. “No,” came the answer.

“Then who asked him to descend further?”

“We have no idea,” was the reply from Dhaka.

When the error was detected, both the Boeing 737, coming to Calcutta from Agartala, and the Air India A-320, headed in the opposite direction, were flying at the same altitude: 17,000 feet. They missed each other by the proverbial whisker, officials said.

A radar replay on June 10 showed the blips indicating the two aircraft merging. That happens only when the horizontal distance between two aircraft is 10km or less. This distance can be covered in a minute by jets travelling at approximately 600kmph.

According to the probe panel, set up by the directorate -general of civil aviation, the pilot of the Boeing 737 descended 1,000 feet more than what the ATC had recommended while the other aircraft had maintained the specified altitude of 17,000 feet.

Air India officials said they would check the probe report and take appropriate steps.