Flight services at Delhi’s Indira Gandhi International Airport (IGIA) were thrown off schedule on Friday after a major technical breakdown hit the Air Traffic Control’s (ATC) messaging network, disrupting operations and delaying more than 800 flights. The issue emerged late on Thursday, impacting the Automatic Message Switching System (AMSS) — the backbone that supplies crucial data to the Auto Track System (ATS), which helps controllers generate flight plans. The system was finally restored by Friday evening.

In an advisory, Delhi airport authorities said,
“Operations at Delhi Airport are facing disruption due to a technical problem in the AMSS, which supports ATC’s flight planning process. All airline services are currently experiencing delays. Teams are working to fix the issue as quickly as possible.”

Passengers were urged to check with their airlines for updated timings.

Later in the evening, the Airports Authority of India (AAI) confirmed that the AMSS had been brought back online.
AAI noted that while the system was functional again, some delays were expected until the backlog cleared. Manual flight plan processing had been ongoing since the glitch occurred to maintain safety.

Officials from AAI and ECIL, along with the original equipment maker, worked together to resolve the failure.
“With automated processes resuming, operations are moving toward normalcy,” AAI said.

With the automated system unavailable for much of the day, controllers had no option but to manually input flight plans — a time-consuming process that led to traffic congestion in the skies around Delhi.

Aviation specialist Captain Sharath Panicker explained that the outage forced controllers to decode and enter every flight plan by hand instead of relying on automatic software interpretation.
“This obviously slows the system down and triggers delays,” he said.

Panicker added that the disruption also impacted the Automatic Terminal Information System (ATIS), which compiles weather data from across India.
“Even weather updates that pilots routinely depend on had to be added manually,” he said, describing how the snag compounded pre-departure delays.

Once aircraft were airborne, he said, the impact was minimal — but getting them off the ground took far longer.

A senior official confirmed the trouble originated within the AMSS itself.
“Controllers are manually preparing flight plans, and it is significantly increasing workload and delay times,” he said.

IGIA — India’s busiest airport with over 1,500 daily movements — saw operations slow dramatically. By 9 am, data from Flightradar24 showed average departures running 45–50 minutes late.

Airlines such as IndiGo, SpiceJet and Air India issued notifications warning passengers of likely delays.
IndiGo said the ATC technical problem was affecting its flights, while SpiceJet mentioned potential delays to both arrivals and departures. Air India apologised for the inconvenience and said its staff was assisting customers.

Inside terminals, travellers queued for hours, many complaining on social media about repeated changes to departure timings and long waits onboard aircraft without clear updates.

Airport technicians continued to work through the afternoon, but officials cautioned that it would take time to clear the pile-up of flights. The disruption also caused cascading delays at airports in Mumbai, Chandigarh, Jaipur, Lucknow and Amritsar.