New Delhi/Mumbai, Jan. 21 -- As IndiGo, the country's largest airline by market share, announces its December-quarter earnings on Thursday, the focus will be on the operational disruptions last month that unsettled passengers, regulators, and investors alike.

The airline, with 63% market share, cancelled about 4,500 flights in the first week of December as it scrambled to adjust schedules to comply with revised flight duty time limitation (FDTL) norms for pilots. The disruption, which stranded hundreds of thousands of passengers, raised questions about IndiGo's market dominance.

Investor unease deepened after civil aviation minister K. Rammohan Naidu vowed strict action as these flight cancellations disrupted travel plans and practicall...