Yechury, who is the chairman of the Parliamentary Standing Committee on Transport and Tourism, said the incident had jeopardised passenger safety and security. “I am sure you will agree with me that this is a very serious matter not only jeopardising air-traffic control with all its horrific consequences, but this also has serious security implications for the country,” Yechury is said to have written in the letter.

He said in the wake of the Mumbai terror strikes, such an incident “requires a probe thoroughly from all angles”. The CPM leader urged Civil Aviation minister Praful Patel to treat the matter seriously and order an urgent inquiry.

Executive director of the Kolkata airport, PK Singhal, however, said the problem was caused due to a glitch in the air-borne equipment of the Jet flight from Bangkok to Kolkata. “Apparently, it was a technical problem and we have reasons to believe the equipment on the aircraft had developed a snag,” said Singhal.

Sources in the ATC said the DGCA has begun a comprehensive probe into the incident and that terror attack angles were also being looked at. “All recorded conversations between the seven flights and the Kolkata ATC are being used to look into the circumstances and the action taken during the incident. And all ATC equipment are also being thoroughly checked to see if it was a fault on the part of Kolkata ATC,” said an ATC official.