The aviation regulatory body said that both airlines failed to deploy pilots trained for Category-III Instrument Landing System (CAT-III ILS) landings, a crucial requirement during low-visibility conditions caused by fog.

This lapse in compliance resulted in the diversion of multiple flights, inconveniencing passengers and raising concerns about the airlines' preparedness for adverse weather conditions.

"They have been asked to submit their response within 14 days," a senior DGCA official said.

The CAT-III ILS is an advanced technology that enables aircraft to land with minimal visibility, making it essential for safe and efficient operations during foggy weather. Airlines are mandated to ensure that a sufficient number of their pilots are trained and certified for CAT-III ILS landings to mitigate the impact of adverse weather conditions on flight schedules.

Delhi Airport currently has only one CAT III-equipped runway designed for operations in low visibility. The second runway, 28/10, is undergoing re-carpeting, affecting its usability. Once the re-carpeting process is completed, the DGCA will inspect the runway for recertification as a CAT III B-compliant runway.

Between December 25, 12 a.m, and December 28, 6 a.m, a total of 58 flights, predominantly operated by domestic carriers, experienced diversions due to low visibility, as per airport sources. The majority of these flights faced cancellations as pilots lacked the necessary training to operate in challenging low-visibility conditions. Specifically, IndiGo witnessed 13 diversions, Air India 10, SpiceJet 10, Vistara 5, Akasa Air 3, and Alliance Air 2 at Delhi Airport during this period.