New Delhi, Dec. 6 -- IndiGo, India's largest airline, is grappling with a cascading operational crisis that has forced the cancellation of more than 1,500 flights a day since Tuesday, as staffing shortages collide with newly imposed crew regulations.

The disruptions have left passengers across major hubs, including Delhi, Hyderabad, Bengaluru and Kolkata, confronting hours-long delays and sharply rising fares.

Amid mounting frustration, sources said the Directorate General of Civil Aviation has summoned IndiGo's senior leadership to account for the turmoil and present a plan to stabilise operations.

As a result of the fewer numbers of flight connecting domestic routes, fares have shot up to 4-5 times normal rates.

The cheapest non-Indig...