Explained: Delhi Airport Tech Glitch That Delayed Nearly 800 Flights

Nearly 800 flights were delayed at the Delhi airport, India's busiest, after a major technical glitch hit its Air Traffic Control (ATC) system on Thursday evening, disrupting flight planning and causing a ripple effect across multiple airports.

The issue originated in the Automatic Message Switching System (AMSS), a key system that supports the ATC's data network, forcing air traffic controllers to process flight plans manually.

Officials described the situation as "unprecedented," saying such a glitch "has not happened earlier."

The Airports Authority of India (AAI) has said that flight operations at Delhi's Indira Gandhi International Airport have stabilised after a technical fault in the Automatic Message Switching System (AMSS) disrupted services on Thursday.

In a statement, the AAI said that the glitch, detected on November 6 in the IP-based AMSS system, had caused delays in the processing of flight plan messages for the Air Traffic Control (ATC). The system has since been restored and is "up and functional now," the authority confirmed.

"Immediately after the fault was identified, a review meeting was conducted by the Secretary, Ministry of Civil Aviation, along with the Chairman of AAI, Member (ANS), and other senior officials. Necessary directions were issued to address the issue," the AAI said.

The organisation added that the Original Equipment Manufacturer (OEM) was engaged to assist with rectification, while additional staff were deployed to manually process flight plans to ensure uninterrupted and safe air traffic operations during the downtime.

A team comprising officials from Electronics Corporation of India Limited (ECIL) and AAI remains on site to monitor the system's performance.

"The AMSS systems are up and functional now. Due to some backlog, there may still be minor delays in the normal functioning of automated operations, but the situation will return to normal soon. We regret the inconvenience caused to airlines and passengers," the AAI said.

What Is AMSS?

The Automatic Message Switching System (AMSS) is a critical part of India's air traffic management network. It automatically receives, processes, and routes flight plan data, which is detailed information filed by airlines before every take-off, to controllers across the country.

At Delhi's Indira Gandhi International Airport (IGIA), which handles over 1,500 flight movements daily and nearly 70 per hour, the AMSS feeds real-time data to the Auto Track System (ATS). This allows controllers to monitor aircraft routes, altitudes, and timings with precision.

When the system crashed on Thursday evening, controllers lost access to automated flight plan data. Every flight plan, which includes routing, fuel, altitude, and weather parameters, had to be generated manually, a process that takes several minutes per flight. With hundreds of aircraft scheduled every hour, operations slowed sharply.

How Did The Glitch Happen?

Sources told NDTV that the problem was first noticed on Thursday evening, when ATC officers reported missing flight plan data on their terminals. Within minutes, controllers realised that the AMSS had failed, halting automatic message flow.

NDTV has learnt that since the controllers were not receiving flight plans automatically on their screens, airlines have been preparing them manually. The system stopped sending data to the auto track system.

The Airports Authority of India (AAI) said in a statement, "Technical teams are working to restore the system at the earliest. Such a glitch is uncommon and has not happened earlier."

Widespread Impact On Flights

Delhi's IGI Airport, among the world's top 10 busiest, saw hundreds of flights delayed through Thursday night and into Friday. According to flight-tracking service Flightradar24, 513 flights were delayed on Thursday, and by Friday, nearly 800 flights had been delayed.

Average departure delays hovered between 45 minutes to an hour, while arrivals were also delayed due to limited parking bays and airspace congestion. Officials said the cascading effect could "take several hours to normalise even after full restoration."

Chaos At Delhi Airport

Since each task before a flight departure is now being done manually, the airport is seeing massive chaos. Thousands of passengers were stranded inside Delhi's terminals by Friday evening. Many waited for hours as departure boards showed repeated delays. Queues formed at check-in counters and boarding gates, with passengers seeking updates from airline staff.

Several travellers reported on social media that they were held on board aircraft for extended periods before take-off. Airport staff distributed refreshments and arranged updates through announcements.

Airlines Issue Statements To Alert Passengers

All major airlines, including IndiGo, Air India, SpiceJet, Akasa Air and Air India Express, were affected by the outage. Some deployed additional staff to coordinate with ATC directly.

An Air India Express spokesperson said, "A technical issue with Air Traffic Control in Delhi has impacted flight operations across all airlines, including Air India Express. Our teams are actively assisting guests at the airport and working closely with the authorities to minimise delays."

Air India Express, which operates about 60 domestic flights and four international services daily from Delhi, advised passengers to check their flight status on the airline's website or mobile app before heading to the airport.

IndiGo, in an advisory on X, said: "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 the inconvenience and appreciate your patience."

Air India also acknowledged the disruption, saying: "We regret the inconvenience caused by this unforeseen disruption, which is beyond our control. Our cabin crew and on-ground staff are assisting passengers. Please check your flight status before heading to the airport."

The effects of the glitch were also felt at several airports, including Hyderabad, where several flights were delayed as ATC operations slowed.

In Hyderabad, flight-tracking data showed that at least 21 flights between Delhi and Hyderabad, 11 arrivals and 10 departures were delayed between 8 am and 8 pm on Friday. Most of the affected flights were operated by IndiGo, followed by Air India and Akasa Air.

What Officials Are Saying

AAI officials said that while such technical issues are rare, the safety of flights was never compromised. "There was no impact on aircraft already in the air. The disruption was purely related to the pre-departure message flow and flight plan processing," an official explained.

They confirmed that the root cause appears to be a malfunction in the central AMSS software, which handles message routing between airports.