Air India has been forced to cancel four international flights after more than 100 pilots called in sick on Monday evening, mounting what civil aviation minister Ajit Singh has called an "illegal" strike.
A spokesman for the flag carrier told news agencies that the Air India pilots were protesting the decision not to grant them exclusive training rights for the Boeing 787 Dreamliner.
Pilots with merger partner Indian Airlines, which was absorbed into the flag carrier in 2007, will also receive training for the 787 - a move which the striking pilots claim will hurt their career prospects.
"They are reporting sick. They have not given any notice for any strike," Singh is quoted by The Hindu newspaper as saying. "So whatever the Air India management rules and regulations, action will be taken accordingly."
Three flights from New Delhi to Toronto, Chicago and Hong Kong have been cancelled so far today (8 May), along with one flight from Mumbai to New Jersey.
Air India has orders for 27 787s, according to Flightglobal's Ascend Online database, with the first two due to arrive in June. The heavily indebted flag carrier recently negotiated a $5.8 billion bailout loan from the Indian government, and is restructuring $4.2 billion of loans from 19 lenders.
In January, 52 Air India flights were cancelled after pilots went on strike over alleged non-payment of salaries. Pilot strikes also led to widespread cancellations in April 2011.