Delhi airport flight chaos: Easterlies, VIP movement & GPS spoofing trigger air traffic congestion

NEW DELHI: Despite all four runways being operational, IGI Airport witnessed significant air traffic congestion on Tuesday evening and some incoming flights had to be diverted to Jaipur. Flight tracking site Flightradar24 listed the city airport in the second spot on Tuesday night on its global list of airport disruptions, with Kathmandu topping the list. At least seven flights of IndiGo and Air India alone were diverted.

Several pilots and air traffic controllers said delays were primarily due to the wind flow changing to easterlies when aircraft land from the Dwarka/Gurgaon side and take off towards Vasant Kunj. The situation was aggravated by some VIP flight movements.


Sources say GPS spoofing was also happening, "distracting" pilots. "Most aircraft follow GPS-based area navigation arrivals and departures. When spoofing happens, it degrades the navigational capabilities of an aircraft. In times like this, the onus of maintaining separation falls on air traffic controllers, leading to excessive workload and exchange of communication between cockpits and ATC," said senior pilots. Spoofing corrupts GPS signals and gives a wrong indicator to pilots of their actual position. A plane may be flying over Baghdad and spoofing could show it's over Ankara, a pilot explained.

IndiGo issued a travel advisory on X at 8.11pm. "Due to air traffic congestion in Delhi, flight operations are currently impacted... extended wait times, both on the ground and onboard, may cause inconvenience, and we sincerely appreciate your patience…"

IGIA has four runways, but they don't have independent flight movement — aircraft movement on one is dependent on movement on others. For instance, when an aircraft is landing on runway 10 and is 1.5 minutes or 2-2.5 nautical miles away from touchdown, no aircraft is cleared to take off from runway 9 until the former has touched down and there's no possibility of it going around.

When westerlies blow — planes landing from the Vasant Kunj side and taking off towards Gurgaon, the spacing between aircraft is reduced and hourly runway capacity is more. The four runways then can handle 42-44 arrivals plus 40-42 departures per hour or a total of up to 85-86. During easterly time, the capacity drops and they can handle up to 37 arrivals plus 40-42 departures per hour or a total of up to 80-81 flights per hour.

This winter, IGIA is witnessing 1,526-1,550 daily flights. "When a VVIP movement happens, for a few minutes, flight movement from all other runways is impacted. Such closures lead to flights stacking up. A half-hour closure, for instance, can lead to a backlog that may take three-four hours to clear," said a source.