As many as 36 flights in Delhi and 10 in Mumbai were cancelled after around 600 Air India pilots, who had been with the erstwhile Indian Airlines, struck work to demand pay parity and better working conditions, officials said on Wednesday.

According to Air India, 12 percent of its total flights have been cancelled. The number is 36 in Delhi and 10 in Mumbai.

The strike was called on Tuesday midnight. The airline management have engaged 150 management and executive pilots to operate the flights, official sources said.

The striking pilots, owing allegiance to the Indian Commercial Pilots Association (ICPA) of the former Indian Airlines, which merged with Air India later, have struck work demanding parity in pay with the Air India pilots and other issues related to work conditions.

Meanwhile, the flag carrier has termed the strike as illegal, and said that ICPA had earlier given assurance to the Delhi High Court that they will not go on strike. The pilots association was also de-recognised and had its offices sealed.

"ICPA has proceeded on strike despite pendency of proceedings in conciliation and their assurance to Hon'ble Delhi High Court. The strike is therefore not legal," said a senior Air India official.

According to the official, negotiations to resolve the ICPA's issues were on and that even in the case of its failure, the pilots association could have further appealed in the (Labour Commission) tribunal, which they already did once.

"No strike is legally permitted during the pendency of the case before the Tribunal," the official said.

Some time ago, Air India had initiated steps with regard to the demands raised by the pilots about parity of pay and working conditions, the official said.

Civil Aviation Minister Vayalar Ravi had appointed a four-member committee, headed by former Bombay High Court judge Justice C.S. Dharmadhikari, to look into all issues in a consolidated manner.

"The committee report is expected in around three months. We feel that the pilots should have waited for the submissions in it before resorting to agitational methods," the official said.

ICPA on its part apologised to passengers, but said that they will not go off-strike until Prime Minister Manmohan Singh or Vaylar Ravi intervene.

"It is the management that has forced us to go on strike, we are the third union to get de-recognised," said ICPA general secretary Captain Rishab Kapoor.

ICPA further said that they get threatened by the management if pilots express their view in public and make enquiries on pay and other issues through RTI (Right to Information) applications.

"We want this mismanagement to come to an end so that it becomes a better environment not just for us, the employees, but for all the travellers," Kapoor said.

Air India said that majority of passengers of cancelled flights were accommodated in other flights.

However, according to 24-year-old Nithi Nigam, who had to travel from Delhi to Mumbai on AI 659, there was no information from the airlines about the flight being cancelled.

"It's shocking. There was no information from the airline. I arrived here at T3 and got to know that the flight has been cancelled. There are others as well who had to face a similar situation."

Similarly, scores of passengers bound for various destinations were compelled to cancel their travel plans.

Families proceeding on vacation were seen making frantic enquiries for booking tickets with private airlines, which have already reported full bookings in view of the summer holidays.

However, leading low-cost carrier SpiceJet has offered to accommodate Air India passengers.

"Passengers need all possible support from the aviation industry to ensure that their travel happens with minimal disruption and their faith in Indian Aviation is maintained," said Neil Mills, chief executive, SpiceJet Limited.