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A critical failure in the air traffic control communication system at Indira Gandhi International Airport (IGI) on Thursday evening disrupted over 800 flights, stranding passengers and forcing airlines to scramble with manual procedures.
The breakdown began at 6:45 p.m. on November 6, 2025, when the Automatic Message Switching System (AMSS) stopped functioning. The AMSS is the central node that routes flight plans, departure clearances, weather data, and coordination messages between controllers, pilots, and airline operations centres. Its failure blocked automated message delivery across all four runways and both domestic and international terminals.
Airports Authority of India (AAI) technicians confirmed the outage stemmed from a corrupted data queue in the AMSS server cluster. Peak-hour traffic - over 90 movements per hour, possibly triggered a memory overflow, halting message processing. Without automated routing, controllers reverted to direct radio and telephone coordination, reducing runway throughput by 60 percent.
From 7:00 p.m. Thursday to 2:00 a.m. Friday, 812 flights were delayed, with average ground holds of 75 minutes. IndiGo reported 342 affected services, Air India 218, and Vistara 109. Fifty-two flights were cancelled, including 18 international departures. Terminal 3 check-in kiosks displayed error messages, and departure boards froze for nearly three hours.
Engineers isolated the faulty server at 11:30 p.m., switched to a redundant unit, and reloaded flight data from backup logs. Full AMSS functionality returned at 4:15 a.m. Friday. By 6:00 a.m., all runways operated at normal capacity, though residual delays cleared only by 10:00 a.m. No aircraft safety was compromised; manual separation standards were strictly applied. The AAI logged zero runway incursions or loss-of-separation events.
Delhi airport handled 1,378 flights on Thursday, close to its daily average of 1,400. The incident exposed single-point dependency in the AMSS architecture, prompting an immediate review of load-balancing protocols. AAI engineers have scheduled firmware patches and additional failover nodes by November 15.
"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, further adding that the Original Equipment Manufacturer (OEM) was engaged to assist with rectification, while additional staff were deployed to manually process flight plans. “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.
