The three Indian Air Force (IAF) choppers carrying President Pratibha Patil and her entourage had landed without clearance even as an Air India aircraft was readying for take off, an investigation into the near-collision at Mumbai airport has found.

The joint investigation team constituted Feb 19 to investigate the near-collision Feb 9 at Mumbai Airport was submitted June 23, as was reported by IANS.

In a statement Wednesday, the government said the coordination among various agencies was unsatisfactory and that the three IAF choppers landed without the Air Traffic Control's permission.

The investigations also revealed that the three choppers were not equipped with safety equipment that are generally installed on helicopters used for civilian purposes.

Soon after the incident, the then Air Chief Marshal Fali Homi Major had given his pilots a clean chit, saying they were among the best in the air force.

'There was a difference of opinion and understanding about the VFR circuit (route procedure) to be followed especially for helicopters between Indian Air Force and Airports Authority of India (AAI),' said government said.

The Directorate General of Civil Aviation, the sector's watchdog, has also made it clear to the IAF that currently there is no need to close airport for VVIP flights.

The DGCA has recommended that AAI and IAF designate senior level officers for effective coordination for such movements. This will include a three-minute closure of airspace for VVIP operations, to be worked out in tandem.

It said choppers and aircraft used for VVIP flights must have safety equipment used on similar civil aircraft.