A technical failure at Delhi’s Indira Gandhi International (IGI) Airport on November 6 disrupted India’s air traffic network, delaying nearly 800 flights and forcing controllers to resort to manual coordination in one of the world’s busiest airspaces. The glitch originated in the Automatic Message Switching System (AMSS), which is a core automation platform that processes and routes flight plans across the country’s air traffic network.
The disruption stalled real-time data transfer between controllers and pilots, halting automated flight-plan processing and triggering ripple effects at multiple airports. In a public statement, the Airports Authority of India (AAI) stated that the glitch was “uncommon” and “has not happened earlier”.
Without that connection, air traffic controllers could not access key details such as aircraft routes, altitudes or timings. Each flight plan had to be created and verified manually, a task that takes several minutes per aircraft. With more than 1,500 flights scheduled daily, the slowdown quickly snowballed.
“Without AMSS, we were effectively blind. We could see radar blips but no flight plan data. Controllers were manually verifying each position and giving clearances one by one,” a senior official familiar with the matter tells Forbes India.
According to flight-tracking platform Flightradar24, about 500 flights were delayed on November 6, and by November 7 the number had risen to over 800; departure delays ranged between 45 minutes and 1 hour, with at least 20 flights being cancelled. The congestion in Delhi’s airspace caused a ripple effect across several cities. For instance, Ahmedabad airport saw around 70 flight delays and six cancellations. By Friday evening, many passengers were stranded inside Delhi’s airport terminals as airlines scrambled to rearrange departure slots.
When the AMSS failed, these automatic transfers of information stopped. “Flight-plan data had to be manually keyed in and cross-verified—which is not unsafe, but extremely time-consuming at this traffic density,” the same official explains.
The AMSS used in Delhi and other major airports has been in service for over a decade. In July this year, the Air Traffic Controllers’ Guild (India) wrote to Parliament’s Standing Committee on Transport warning that the automation systems were “showing performance degradation including slowness and lag”. The letter was written soon after an Air India plane crashed, killing 241 passengers and 19 on the ground on June 12. It urged the government to upgrade automation infrastructure to match global standards, such Federal Aviation Administration’s (FAA) in the US and Europe’s Eurocontrol. The Parliamentary Committee recommended that India’s air traffic systems be modernised with predictive tools and artificial intelligence–based conflict detection.
While it is unclear when Delhi’s AMSS was last upgraded, the senior official says that the hardware had already “outlived its service life”. The process of replacing such systems typically takes two to three years, and no such process has started so far.
When GPS signals become unreliable, pilots switch to ground-based navigation aids such as Very High Frequency Omnidirectional Range (VOR), which help aircraft determine their position through radio signals transmitted from fixed stations. “Controllers assist pilots by providing headings until the aircraft’s systems re-stabilise,” the senior official says. “VORs act as a backup when GPS data cannot be trusted.”
The National Security Adviser’s Office, led by Ajit Doval, has initiated an inquiry into whether spoofing activity coincided with or worsened the AMSS disruption. “When GPS started showing false coordinates, it created a double challenge: Signal errors in the air and data loss on the ground,” the official adds.
A joint team from AAI, ECIL and the Ministry of Civil Aviation continues to monitor the system’s performance. “The AMSS systems are up and functional now,” AAI said in a statement on November 8. “Due to some backlog, there may still be minor delays, but operations will return to normal soon.”
ECIL and AAI did not respond to requests for comment by the time of publication of this story.
First Published: Nov 11, 2025, 18:28
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