The air force, already facing flak over the high accident rate of its fighters, seems to have a new problem at hand.

There are problems with the IAF's ammunitions or trigger mechanisms, according to sources. "We are yet to zero-in on the precise problem," says an officer.

In the run-up to 'Vayu Shakti', the IAF's biggest firepower demonstration since the Kargil conflict, it has lost two pilots and their planes, and at least one Su-30MKI has escaped disaster.

According to officials, during the rehearsals on March 7, the Su-30MKI fired an R-73 air-to-air missile at a flare in the air. But instead of hitting the target, the missile flew a few feet and fell to the ground and exploded.

On February 7, a MiG-23 crashed in the Pokhran range, killing Flight Lieutenant Bharat Kumar. The IAF is yet to make public the reasons behind the incident, but witnesses report seeing a blast.

Similarly, on February 26 Wing Commander Ravi Khanna, commanding officer of a Jaguar Squadron, also died after his plane exploded.

In the above two cases, it is believed that the ammunition did not leave the planes after being fired.

Suspecting a problem with its indigenously developed trigger mechanism, the IAF has called in a team of experts from the Pune-based Armament Research and Development Establishment.

There is no conclusive evidence that the trigger mechanism was at fault, says a source close to ARDE.

He says among the causes that the IAF is looking at is the fact that it was using old ammunition, "but not expired ones", for the   rehearsals.

Whatever the case maybe, the IAF has another headache.

"We will take necessary steps based on the report of the court of inquiry now underway," says an official in New Delhi.