New Delhi: A recent air-miss incident involving a special aircraft carrying UPA Chairperson Sonia Gandhi and a Virgin Atlantic flight is being probed by the Directorate General of Civil Aviation (DGCA).

Maintaining that the incident was not one which could have resulted in a mishap, official sources said it was, however, a "procedural breach" of regulations laid down for lateral and vertical separation between two aircraft flying at a certain height. This had resulted in what is called an "air-miss" as opposed to "near-miss". They said the investigation would be completed in about a week.

Asserting that there was never a possibility of a mid-air collision, the sources said no airport on the route of these two aircraft, then flying over Punjab, reported any TCAS (traffic alert and collision avoidance system) warning. Elaborating on the September 10 incident, the sources said Gandhi was returning to the capital from Srinagar in a VIP jet, a Boeing 737 of the IAF, when it came close to Virgin's Airbus A-340 plane coming from London.

The "breach" occurred when the two aircraft came close at a vertical separation of 1,000 feet, instead of 2,000 feet. According to guidelines, planes that are flying at over 29,000 feet and are RVSM (Reduced Vertical Separation Minima) compliant could fly at a vertical separation of 1,000 feet.

However, it was found that the IAF Boeing was not RVSM-compliant and, therefore, should have maintained a separation of 2,000 feet, the sources said. They said the flight data recorder and air traffic control records are being checked as part of the inquest being carried out by the DGCA.