Upset over non-payment of salaries, about 40 Air India pilots reported "sick" on Saturday, leading to numerous cancellations of flights and leaving thousands of passengers stranded.
The government pleaded with the pilots to return to work, saying it was studying their demand.
Twenty-eight flight cancellations were reported in Delhi alone and three in Mumbai, the country's two busiest airports.
The cancellations in Delhi began right at dawn and continues well over noon, an Air India official told IANS. "Nearly 40 pilots have called in sick," he added.
Civil aviation minister Ajit Singh urged the employees to join back and promised to discuss their problems with finance minister Pranab Mukherjee and petroleum minister S. Jaipal Reddy Tuesday.
The talks will be aimed at improving the carrier's financial status, which has left pilots without salaries for two months. Most components of the pay have not been paid for over four months.
"We are looking into the problem. The pilots did not give any notice... We know the pilots have problems and their salaries have not been paid and are under financial stress," the minister said here.
He added that the airline management was talking to pilot unions.
Passengers stranded at the airports -- particularly in Delhi -- were furious.
"My Kolkata-bound flight at 9 was cancelled. I reached the airport a little after 7 but I was not informed that my flight has been cancelled," complained Arun Gupta.
One estimate put the number of stranded passengers at around 4,000.
Air India pilots and other staff have not been paid salaries for November and December.
Performance-linked incentives, which constitute 20-60 percent of the total pay package, too have not been paid for four months.
The airline official said the mandatory notice by the pilots for going on sick leave was not served on the carrier.
"We are in talks with some pilot leaders in Delhi. We are taking all possible steps to help passengers like providing them flight information, getting them transferred to other airlines and providing them refunds," the official said.
The Indian Commercial Pilots Association (ICPA), which mainly comprises erstwhile Indian Airlines pilots, has asked the pilots to return to work.
"The management has to initiate immediate steps to rein in the situation. We are not part of the protest but we understand their problems," an ICPA spokesperson said.
On Friday, Air India chairman and managing director Rohit Nandan said in a that employees' dues for November would be paid by Saturday.
The carrier currently has a total debt of Rs.43,777 crore, including loans and dues it owes to vendors like oil firms and airport operators.ICPA asks agitating pilots to return to work | 'Will take time to solve issue'