Indian regulators said Monday they would check that thousands of pilots were qualified to do their job, after at least four were alleged to be flying passenger planes with forged qualifications.

In the latest case, a male pilot working for national carrier Air India was arrested on Sunday over allegations he had used fake documents to gain his flying licence.

The country's director general of civil aviation, Bharat Bhushan, told the CNN-IBN television news channel that 4,000 licences would now be checked.

The first allegations came to light last month, when the DGCA revoked the licence of a female pilot at IndiGo airlines who was found to have forged papers to get her airline transport pilot licence.

The pilot's qualifications and record were scrutinised after she caused damage to an Airbus A320 aircraft by landing the plane on the nose wheel instead of the rear wheels.

"We could see there were some deficiencies in her landing technique," Bhushan told CNN-IBN on Monday. "She had achieved the licence on the basis of marksheets which were not authenticated.

"We took a detailed investigation and as a result more names have come up."

Two pilots flying for IndiGo and MDLR airlines also lost their licences after the DGCA found out that they were flying as captains without passing their tests to graduate from co-pilot.

Rising incomes and the liberalisation of the airline market in the 1990s have led to an explosion in air travel in India, with passenger numbers up 25 percent over the last 12 months.

With new routes and new aircraft being regularly inducted, the half-dozen low-cost Indian airlines are competing fiercely for pilots.