Several Air India flights from Mumbai’s Chhattrapati Shivaji Maharaj International Airport were delayed on Thursday following a flash strike by the contractual workers of Air India Air Transport Services Limited, The Indian Express reported.

The ground staff began their strike at 11 pm on Wednesday demanding a bonus for Diwali. They also demanded the reinstatement of three employees who were fired, Business Standard reported.

An Air India official said 10 domestic and three international flights were delayed because of the strike on Thursday morning, PTI reported. Negotiations between Air India Air Transport Services Limited and its striking workers are under way.

“Due to a sudden industrial situation at Mumbai by AIATSL employees, some flights have got delayed,” an Air India spokesperson said. “We are assessing the situation and all efforts are being made to minimise delays or disruption. Air India staff have been called from home to help with passenger check-ins.”

The airline’s permanent employees have been deputed to normalise the flights, the spokesperson said, according to ANI. “