New Delhi, A major technical glitch at Delhi’s Air Traffic Control (ATC) on Friday, November 7, 2025, triggered a wave of delays across India, affecting hundreds of flights and thousands of passengers. The problem was traced to the Automatic Message Switching System (AMSS), a core back-end service that supports ATC with flight-plan messages. When AMSS faltered, controllers moved to manual processing, slowing departures and creating a nationwide ripple effect. Authorities said on Saturday that the issue was resolved and operations were returning to normal, though schedules were still clearing the backlog.
Through Friday, numbers fluctuated as airlines updated their schedules. Several outlets reported 300 to over 800 delayed flights and a smaller number of cancellations. Some airports outside Delhi—Ahmedabad, Mumbai, Jaipur, Lucknow, Patna, Vadodara—reported knock-on delays as aircraft, crew, and gates cycled more slowly. The Airports Authority of India (AAI) said technical teams worked to restore AMSS, while the airport operator, Delhi International Airport Ltd. (DIAL), told passengers on Saturday that AMSS was improving and operations were stabilising.
What failed and why it mattered
AMSS is the digital post-office for flight plans and related messages. Every few seconds, it sends and receives structured data for controllers. If this message flow slows or stops, controllers must type, check, and pass flight plans manually. That is safe but slow. When the rate of departures falls at a major hub like Delhi, the delay spreads quickly through the network because the same aircraft and crew are scheduled to operate multiple flights in a day.
Inside the terminals
Passengers reported long queues at check-in and security, crowded boarding gates, and frequent gate changes. Airlines urged customers to arrive early and monitor apps for re-timed departures. Families with children and elderly travellers were advised to seek assistance at helpdesks. With the system back up, many flights still departed late on Saturday morning as airlines repositioned aircraft and crew.
Safety and procedures
Aviation systems are designed with fallback modes. When a non-separation system like AMSS hits trouble, the default is to slow down rather than take risks. Controllers rely on manual workflows, which keep aircraft safely spaced but reduce throughput. There has been no official indication that core safety systems were compromised. Media commentary referenced broader concerns about cyber risks and GPS interference globally, but officials have not published any detailed public attribution beyond a “technical issue” at the time of writing.
Recovery and next steps
By Saturday, November 8, the airport said ops were returning to normal. Airlines began adjusting arrival and departure times to ease congestion during peak banks. Even after a fix, networks take time to reset: aircraft must complete their current rotations, crews must remain within duty limits, and maintenance windows must be respected. A full return to the pre-glitch timetable can take several rotations.
What this incident shows
India’s air network has grown rapidly. A single technical bottleneck can now affect hundreds of services. The incident highlights the importance of:
- Redundant architecture and failover drills for critical systems;
- Clear, time-stamped passenger communication through official channels;
- Data-security and resilience in aviation IT; and
- Network planning tools that can quickly re-balance schedules after a shock.
Advice for travellers
If you’re flying in the next 24–48 hours, check your flight status before leaving home, build in extra time, and keep boarding passes and receipts. For missed connections, call your airline to protect the onward sector. Rebooking and refunds depend on fare rules and the cause of delay; many airlines treat ATC/airport technical failures as extraordinary circumstances, but service recovery (meal vouchers, hotel in long delays) may be offered case-by-case.
Official words
The airport advisory on Friday cited an “ongoing technical issue with AMSS.” AAI said controllers were processing flight plans manually and technical teams were working to restore services. On Saturday, the airport said AMSS was improving and operations were returning to normal. IndiGo said it would adjust arrivals and departures to stabilise the schedule and asked customers to watch for updates on its digital channels.
FAQs
Q1: What exactly failed at the Delhi Airport, and what does it do?
The system that failed is the Automatic Message Switching System (AMSS). Think of it as the airport’s central nervous system for communication. Its job is to automatically and instantly send vital messages—like a pilot’s request to take off, weather warnings, or a flight’s final arrival time—between the Air Traffic Control (ATC), the planes in the sky, and other airports across the country and the world. When the AMSS failed, this automatic link broke. Controllers were forced to use slower methods like telephones and written messages, similar to how air traffic was handled decades ago, which is far too slow for a modern, high-volume airport like Delhi.
Q2: Why did a Delhi glitch affect flights in other cities like Mumbai and Bengaluru?
This happened because of the “hub-and-spoke” nature of air travel in India. Delhi Airport (IGI) is the country’s main hub, meaning most domestic flights connect through Delhi to reach other major or smaller cities, and nearly all international flights pass through Delhi’s airspace. When Delhi’s ATC capacity slowed down, controllers at other cities (the “spokes”) like Mumbai, Hyderabad, and Kolkata had to hold their flights or delay their departures. They did this to prevent air traffic congestion above Delhi and to avoid leaving planes stranded without a clear landing slot, thereby spreading the chaos nationwide.
Q3: Were there any safety risks involved during the manual operations?
The immediate safety risk was managed by drastically reducing the number of aircraft allowed to take off or land. When the system went manual, the number of operations (take-offs and landings) per hour was cut down significantly. While this caused massive delays, it is the standard and safest procedure to ensure that no mistakes occur in manually tracking and guiding planes. Air traffic control is highly trained, but the slower pace prevents human error when managing complex tasks with paper and voice instead of automated radar-based systems.
Q4: Who is responsible for fixing this, and what are the long-term solutions?
The immediate repair and restoration fall under the Airport Authority of India (AAI), which manages the ATC infrastructure, and the Ministry of Civil Aviation (MoCA), which provides oversight.
For a long-term solution, experts are calling for:
- System Redundancy: Installing a complete, mirror-image backup AMSS system that can take over instantly if the main one fails.
- Modernisation: Upgrading old software and hardware with the latest international standards to prevent glitches.
- Regular Audits: Mandatory, external safety audits of all critical airport communication and navigation systems.
Q5: Can passengers claim compensation for these delays and cancellations?
Airlines generally follow the DGCA guidelines for passenger rights. While flight cancellations and delays due to “major technical snags” are sometimes classified as extraordinary circumstances (which may limit monetary compensation), passengers are usually entitled to:
- Full Refund if they choose not to travel.
- Alternative Flight without extra charge.
- Meals and Refreshments for long delays.
- Accommodation (if delayed overnight and not residing locally). It is advisable for affected passengers to keep all booking records and contact their specific airline for the applicable policy.