Indian airline Vistara, co-owned by Tata Group and Singapore Airlines Ltd., has canceled dozens of flights after pilots called in sick en masse over plans to cut their pay, according to a person familiar with the matter.

The airline is changing its pay structure to bring it in line with Air India Ltd., which is in the process of merging with Vistara, said the person, who asked not to be identified because the information isn’t public. That will see pilots’ guaranteed pay reduced to 40 flying hours from 70 hours, the person said.

The shortage of staff has seen Vistara cancel more than 85 flights since Monday, according to FlightAware data. It typically operates more than 300 flights a day.

“We have had a significant number of flight cancellations and delays in the past few days due to various reasons including crew unavailability,” the company said in a statement. The airline will deploy larger aircraft, like Boeing Co.’s 787 Dreamliner and Airbus SE’s A321neo, on some domestic routes as it combines flights, it said.

Vistara expects to return to its regular capacity soon and is offering alternate flights or refunds to travelers affected by cancellations and delays, it said. 

The issue has drawn the attention of India’s aviation regulator, which has directed Vistara to submit daily reports about flight disruptions and said the airline must comply with requirements to make provisions for passengers whose flights are canceled or delayed.

Separately, the Ministry of Civil Aviation said it is monitoring the situation but operations are managed by individual airlines.

Pilots’ anger over the pay cut comes as Vistara’s planned merger with Air India inches forward. The deal is expected to be completed by the end of the year and Singapore’s antitrust regulator last month granted conditional approval for the merger.

Singapore Airlines will hold a 25.1% stake in the enlarged airline after an investment of $250 million. Vistara has a fleet of 67 aircraft, mainly from the A320 family, as well as six 787 Dreamliner jets.