The ATCs are now fully operating the new radar system which has been at the centre of controversy.

"Only the liaisoning work with the Air Force and other airlines is being done with the old system. The entire air traffic control (ATC) is being done with the new system" said Brijesh Shekhar, president, ATC Guild.

He denied that the ATC Guild has picked holes in the system just to get the Airports Authority of India (AAI) to pay attention to its wage increase demands. "All we are demanding is that the system be customised to our needs. Instead of a one-ear headset, we can have a two-ear headset which can permit us to communicate with our colleagues," he added.

Shekhar also admitted that the new system is far better in terms of operation than the earlier one.

The Airports Authority of India (AAI) stressed thatthe Rytheon system was `working fine'. "There is nothing wrong with the Raytheon system" said an AAI spokespoerson.

The Raytheon system was handed-over to the AAI in March 1998. However, it was lying idle as the ATCs had refused to operate the new radar system. The ATCs finally moved to the new complex housing the secondary radar system on January 1 this year.

The secondary radar system is far more sophisticated than the earlier system operated at Delhi airport. In this system, unlike the earlier one, the height of an aircraft, a crucial factor, is automatically calculated.

The secondary radar system works on the basis of a responder on the ground which sends a signal interpreted by the interrogator on the aircraft. The interrogator sends the aircraft identification, height, and other crucial data, to the ATC.

The ATC can then put this data in the automated flight path to guide the aircraft further.

Incidents like the Charkhi Dadri air-crash, where two aircraft collided mid-air, can be avoided withthe secondary radar system.

The Raytheon system ran into a series of controversies before becoming operational. At one point, the AAI was contemplating dragging the US-based Raytheon to Court due to the delays in the implementation of this system.

Both Raytheon and AAI had blamed each other for the delays in setting-up the secondary radar system.