The Capital’s airport was plunged into chaos on Friday when the backbone of air traffic communications was paralysed, disrupting close to 65% of all flights and leaving thousands of passengers stranded with delays stretching beyond 12 hours until authorities managed to restore systems late in the evening.
The Airports Authority of India said late on Friday it had restored the Automatic Message Switching System around 9pm, ending what experts described an “unprecedented” 30-hour outage that forced air traffic controllers at Indira Gandhi International Airport to manually process flight plans — a time-consuming procedure that created cascading delays across India’s aviation network.
In a statement, AAI said the IP-based AMSS system malfunctioned on Thursday, prompting an emergency review meeting led by the civil aviation secretary. Engineers from Electronics Corporation of India Limited worked alongside AAI personnel to restore operations, though officials warned that backlogs would cause lingering delays.
“We regret the inconvenience caused to airlines and passengers,” AAI said, adding that the system is “now up and functional” but automated operations would take time to normalise.
AAI did not respond to requests for comment on what had caused the problem and why backup or redundancy systems, if any, failed to act.
The crisis, which officials speaking on condition of anonymity called the longest such outage on record, rippled through airports in Mumbai, Bengaluru and Chennai—major hubs that connect to Delhi’s 1,500 daily flights.
The system failure began at 3pm on Thursday but its impact became apparent only at 8:30pm, initially affecting 15 flights. By 5:45am on Friday, the disruption had escalated dramatically as the AMSS—the digital backbone that feeds crucial flight plan data to the Auto Track System used by air traffic controllers—stopped transmitting information automatically to controller screens.
Starting Friday, serpentine queues formed inside and outside Indira Gandhi International Airport as clueless passengers showed up only to be informed of inordinate delays. Some passengers faced delays of six to eight hours, while others watched their flights pushed back by over 12 hours. By 11pm on Friday, 978 flights had been affected in all.
Elaborating on the problems the outage created, an official aware of the matter explained that “since the air traffic controllers have not received flight plans automatically on their screens, they are now preparing flight plans manually using available data, a process that is slowing down operations and contributing to congestion at the airport.”
A second official close to the matter said the system had experienced issues “intermittently in the last two days” before significantly impacting operations from Friday morning. The official had earlier said delays were expected to continue “through the night and also tomorrow.”
Widespread impact
All major carriers were affected. 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 said the “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.” Air India Express, SpiceJet and Akasa Air also reported their operations were affected.
It was only by afternoon—by which time airlines had swung into action with text messages and emails to passengers about delays—that things eased up outside the airport. However, the cascading impact had spread to other cities, including Mumbai, Bengaluru and Hyderabad as flights coming from or heading to the Capital from these locations were impacted.
With delays mounting, all stakeholders—including Delhi International Airport Ltd, airlines and the Central Industrial Security Force—held a collaborative decision-making exercise. Delay quick response teams were stationed at all terminals.
Airlines were instructed to coordinate with their destination airports to ensure departures from Delhi aligned with prevailing conditions and to carry sufficient fuel in case of diversions.
A former AAI official said: “This is the first time it is taking so long to resolve a glitch. The AMSS in Delhi has a backup—however, what has caused the issue to remain unresolved is a question to be answered.”
The failure comes amid a spate of concerns and glitches, including alleged GPS spoofing attacks that some reports stated as having been observed in recent days. GPS spoofing involves transmitting false satellite signals that can fool aircraft instrument into miscalculating speed, location and altitude – though pilots typically have a suite of other instruments that act as failsafe for such critical metrics.
The second official cited above reiterated that Friday’s problems was not caused by GPS spoofing or a cyberattack.
A senior official of the ministry of electronics and IT said a cyberattack was not one of the factors being explored.
AAI is implementing a new PAN India ATS Message Handling System to replace existing AMSS infrastructure at all airports. The system is designed to ensure “secure and efficient exchange” of air traffic service messages between air navigation service providers and aviation stakeholders, according to AAI’s website.
However, officials said that while the AMHS has been installed, it has not yet been brought into use.
Aviation expert Mark Martin, of Martin Consulting, said, “If it is for a new system, why didn’t they test it first and why didn’t they test it in small locations and then roll it out in Delhi and Mumbai which is the busiest enroute airspace possibly in the whole of Asia. They should have done it phase-by-phase.”
