Operations of nearly 400 flights were disrupted – both arrivals and departures – at Delhi’s Indira Gandhi International (IGI) Airport following a technical glitch in the Automatic Message Switching System (AMSS) that handles flight plan messages, forcing controllers to process them manually. The Airports Authority of India (AAI) said in a statement that the issue, detected on November 6, caused delays in processing flight data, but the AMSS systems are “up and functional now”.

AMSS is a key communication network that links air traffic control, airports, and airlines. It automatically processes and transmits flight plans, route clearances, and operational updates. When it malfunctions, staff have to handle data manually, which in turn, slows down operations and causes flight delays.

Both the AAI and Delhi Airport confirmed that delays were being experienced due to the AMSS malfunction, which supports Air Traffic Control (ATC) operations. Authorities advised passengers to stay in touch with their respective airlines for the latest updates on flight schedules.

Planes were GPS spoofed

Now, experts have suspected that the Delhi airport has experienced its ever “GPS spoofing” scare, affecting aircraft operations around Delhi.  

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According to a report by India Today, IGI Airport experienced GPS spoofing, due to which several flights were diverted, causing congestion. GPS spoofing involves transmitting fake satellite signals to mislead aircraft about their actual positions – potentially throwing off navigation by up to 2,500 km. 

ILS closure worsened the situation

The situation was aggravated by the closure of the main runway’s Instrument Landing System (ILS), which is currently being upgraded to Category III standards. IILS is a ground-based radio navigation system that helps aircraft during landing. 

Once complete, this will allow landings even during dense winter fog, a long-standing issue at the Delhi airport.

In the absence of ILS, aircraft rely on Required Navigation Performance (RNP), which depends on GPS signals. With GPS compromised, congestion worsened at a time when the airport was already witnessing a spike in traffic – around 1,500 flight movements per day, The Times of India reported.

Delhi airport ranked second for flight disruptions on Tuesday, with at least seven flights diverted to Jaipur and Lucknow, even as all four runways remained functional, TOI reported. 

‘Restore ILS on IGIA’s main runway at the earliest’

The outlet further reported that the Delhi International Airport Ltd (DIAL) aims to restore full ILS functionality on runway 10/28 by November 27.

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“Why GPS spoofing is happening could be a security-sensitive issue, and we don’t want to know why the same is happening. The only thing that needs to be done is having ILS on IGIA’s main runway 10/28 at the earliest,” TOI quoted a source as saying. 

The Navigation Integrity Category value – which measures aircraft positioning accuracy – reportedly dropped from 8 to 0, with most incidents reported within a 60-nautical-mile (110 km) radius of Delhi.

The Directorate General of Civil Aviation (DGCA) has taken cognisance of the GPS spoofing incidents and has launched an enquiry into the incident, The Hindu reported.

Pilots have also been advised to exercise caution while approaching Delhi airspace.

Earlier this year, the Centre informed the Lok Sabha that 465 GPS spoofing incidents had been reported near the India-Pakistan border, mainly in Amritsar and Jammu, between November 2023 and February 2025.

The International Air Transport Association (IATA) recorded 4.3 lakh GPS jamming and spoofing cases over conflict zones in 2024 – a 62% rise from the previous year.