A number of Vistara's pilots went on sick leave, and some of those who went on leave protested a downward revision to pay ahead of a merger with Tata-owned Air India later this year, amid growing fatigue from a busy schedule, Reuters reported earlier this week.

Jointly owned by the Tata group and Singapore Airlines, Vistara has been cancelling flights since late March due to its crew's unavailability.

"We used to operate about 350 flights a day. We are short by about 20 flights or so every day," said Vinod Kannan, Vistara's chief executive, adding that the flights were cancelled "mainly to provide a little more buffer" of available crew and "not for any other reasons".

Some pilots have expressed concerns regarding the full schedule that had pilots fly more...the cancelled flights are to try and provide better rosters, Kannan added.

The airline is likely to look at cutting its crew's schedules for May as "it depends on what kind of preference the pilots have and what kind of buffers we want to take," Kannan added.

(Reporting by Varun Hebbalalu in Bengaluru; Editing by Janane Venkatraman)