Vistara’s crisis intensified today with dozens of flights canceled due to absentee pilots, sources said, who were protesting against the terms of a new contract following the airline’s merger with Air India.

A report by NDTV Profit says Vistara pilots have taken sick leave en masse, a move that comes as a result of salary structure changes the airline is trying to implement ahead of its merger with Air India.

In an email to pilots, Vistara said those who have not signed up for the new pay structure will not receive a spot on the upgrade sequence list. This email has been reviewed by NDTV Profit.

They also were not eligible for the one-time bonus promised to pilots, the email said.

Such pilots will be deemed not interested in working with Air India. “Hence, they will not be involved in the transition to Air India,” Vistara further said.

Several pilots called in sick after receiving the email, disrupting flights, sources said.

The airline, jointly owned by the Tata Group and Singapore Airlines, said yesterday that its teams were working to stabilize the situation.

“Over the past few days, we have experienced a significant number of flight cancellations and delays due to various reasons including crew absences,” a spokesperson for the company said in a statement.

“Our teams are working tirelessly to stabilize the situation. We apologize for the inconvenience these disruptions have caused our valued customers,” the spokesperson added.

Yesterday 50 flights were canceled and more than 160 were delayed, while some 38 flights were canceled this morning.

Post-privatization, Vistara is merging with Air India, with Singapore Airlines acquiring a 25.1% stake in the once state-controlled airline.