Over 900 flights delayed at Delhi as air traffic control system fails: GPS spoofing suspected

NEW DELHI, Nov 8: In a rare and deeply concerning disruption, operations at Delhi’s IGI Airport (Indira Gandhi International Airport) were thrown into chaos this week as over 900 flights were delayed and at least 20 cancelled, following a dual crisis involving a critical systems failure and suspected GPS spoofing—a cyber threat more commonly associated with conflict zones and military deception.

The passengers were stranded for about 12 hours. The system was restored late in the night and the flight operations were limping back to normal on Monday morning. The crisis had gradually affected all the national network. The air traffic controllers had to manually process flight schedules during the downtime. The crisis that began on Thursday afternoon, officially ended on Friday night. It was the longest such outage. There was no redundant systems working, it is learnt. Mumbai, Bengaluru and Hyderabad were badly affected.

The disruption began with a technical failure in the Automatic Message Switching System (AMSS)—a vital component of air traffic control (ATC) that automates the processing of flight plans and communication between pilots and controllers. With the system down, ATC personnel were forced to manually process flight data, significantly slowing down operations and causing a cascading effect of delays and diversions.

Compounding the crisis, several pilots reported receiving corrupted satellite navigation data while approaching Delhi. This was later identified as GPS spoofing—a sophisticated cyberattack where fake satellite signals are broadcast to mislead aircraft navigation systems.

Unlike GPS jamming, which blocks signals, spoofing feeds false coordinates, potentially causing aircraft to misjudge their position.

The technical threat of GPS spoofing

GPS spoofing is not new, but its appearance at a major civilian airport like Delhi’s is unprecedented in India. The technique involves a rogue transmitter mimicking GPS satellites, tricking aircraft into believing they are in a different location etc. This can lead to navigational errors, airspace violations, or even mid-air conflicts if not caught in time.

While modern aircraft are equipped with Inertial Navigation Systems (INS) and multi-sensor fusion algorithms to cross-verify GPS data, spoofing can still cause confusion—especially during low-visibility landings or in congested airspace. The fact that these incidents coincided with easterly wind shifts—forcing aircraft to land from the Dwarka side—only added to the congestion and risk.

Link to recent crashes?

Though no direct link has been established, the Delhi spoofing scare echoes concerns raised after recent aviation incidents globally. For instance, early this week a cargo plane crashed in Kentucky. Past the critical decision speed to abort takoeff, at 30 m above ground level and at a speed of 340 km/h before crashing, a repeating bell sounded in the cockpit for 25 seconds. Another instance is the 2024 near-miss over the Black Sea due to navigation anomalies suspected to be caused by spoofing or jamming.

These incidents have reignited calls for robust anti-spoofing protocols, including cryptographic GPS, ground-based augmentation systems, and real-time anomaly detection.

The Airports Authority of India (AAI) has restored the AMSS system and is investigating the spoofing reports in coordination with cybersecurity and aviation safety agencies.

Meanwhile, aviation experts are urging the Directorate General of Civil Aviation (DGCA) to issue immediate advisories and upgrade ATC resilience against electronic warfare tactics.

As India’s busiest airport and a critical node in global aviation, Delhi IGIA’s vulnerability to such threats underscores the urgent need for cyber-physical security integration in civil aviation. The skies may be clear, but the signals guiding aircraft through them are now under invisible threat. It is reasonabe to suspect foul play in some Indian crashes caused by misleading altitude readings.

IndiGo advisory to passengers: IndiGo, India’s largest airline, warned passengers on X: “Flight operations at Delhi Airport are currently experiencing delays due to a technical issue with the Air Traffic Control system. As a result, flight operations at Delhi and several northern regions are impacted. We understand that extended wait times, both on the ground and onboard, may cause inconvenience.”

Air India: “Technical issue with the ATC system in Delhi is impacting flight operations across all airlines, leading to delays and longer wait times at the airport and onboard aircraft.”

How ground-based GPS spoofing works

GPS spoofing involves broadcasting fake satellite signals that mislead GPS receivers into calculating incorrect positions. A ground-based transmitter can execute this by mimicking legitimate GPS signals with higher signal strength and deceptive timing data.

The sequence

Signal Generation - The attacker uses a software-defined radio (SDR) or GPS simulator to generate counterfeit GPS signals.
These signals replicate the structure of real satellite transmissions but contain manipulated location and time data.
Transmission
The spoofed signals are transmitted from a ground-based antenna, often at a higher power than the weak signals received from actual satellites
Because GPS receivers prioritize stronger signals, they may lock onto the spoofed ones.
Receiver hijack
The aircraft’s GPS receiver begins to calculate its position based on the fake signals.

This can cause:

Sudden shifts in reported location
Incorrect altitude or heading
Loss of synchronization with ATC instructions
Gradual Drift vs. Sudden Jump
Sophisticated spoofers gradually drift the aircraft’s perceived location to avoid detection.
Cruder attacks may cause sudden jumps, triggering alerts in cockpit systems.

Aviation risks

Approach Phase Vulnerability: Aircraft are most vulnerable during landing, when GPS is used for precision approaches (e.g., RNP, LPV).
ATC Conflicts: Spoofed positions can lead to airspace violations, runway incursions, or loss of separation.
Instrument Confusion: Pilots may see conflicting data between GPS, inertial navigation, and radar.

Detection and counter-measures

Multi-sensor fusion: Aircraft systems compare GPS with inertial, barometric, and radio navigation data
RAIM (Receiver Autonomous Integrity Monitoring): Detects inconsistencies in satellite geometry.C
Cryptographic GPS (e.g., M-code): Used by military to authenticate signals.
Ground-based augmentation systems (GBAS): Provide verified corrections to GPS data.

Real-world examples

Black Sea (2024): Multiple aircraft reported spoofed positions over contested airspace.
Middle East (2023–2025): Civilian aircraft near conflict zones experienced spoofing and jamming.
Delhi (2025): Pilots reported corrupted GPS data during approach, possibly due to spoofing from a rogue transmitter or misconfigured ground equipmen

—Agencies