Delhi airport ops resume, but uncertainty remains: 5 unanswered questions

While the Airports Authority of India (AAI) has said that the issue at the Delhi airport was fixed, there is no clarity yet on what caused it.

The Indira Gandhi International Airport, the country’s busiest, saw serpentine queues on Friday after a major technical failure in the air traffic control system delayed more than 800 domestic and international flights, and led to cancellations of 20 flights.

Aircraft waited for takeoff at Indira Gandhi International (IGI) Airport on Friday. Flight operations at the Delhi airport were delayed due to a technical glitch in the Air Traffic Control (ATC) system, which supports air traffic data. (Hindustan Times)

The Airports Authority of India (AAI) later said the issue had been fixed, but warned that some backlogs could continue to affect automated operations before things fully normalize.

Over 800 flights were delayed at the Delhi airport and at least 20 were cancelled.

What happened?

Automatic Message Switching System (AMSS) failed, cutting off automatic transmission of flight plan data to air traffic controllers’ screens.

Controllers had to prepare flight plans manually, slowing down operations dramatically.

A glitch was reported on Friday morning, and by 8.30 pm, 15 flights had been cancelled over 800 had been delayed.

The following operations took a hit due to the glitch:

1. Flight plan updates
2. Real-time weather data
3. Slot decisions: when a flight can depart
4. Gate assignments based on accurate arrival/departure data

The system was finally restored at 9 pm, the Airports Authority of India (AAI) said.

Over 800 flights delayed on November 7

Even as airports systems have returned back to normalcy, some key questions regarding the chaos remain unanswered. Here they are:

1. What caused the outage?

Every time the Airports Authority of India (AAI) shared an update, it only cited a “technical issue” with the AMSS, but there was no clarity on what the issue was or what caused it. The authorities only said that the technical issue caused delays in processing flight plan messages thus causing flight delays.

2. Why did it take so long to restore?

While the first signs of a system failure appeared around 3 pm on Thursday, and flight delays started on Friday morning, it was only at 9 pm that the AAI at Delhi airport said that the issue had been resolved.

Many flights were delayed due to "technical issues" at the Delhi airport on November 7. (HT)

3. What happened to the backup?

Aviation norms require standby systems to be ready at all times. Why wasn’t the backup operational at India’s busiest airport?

4. Who is responsible?

There is still no clarity on which company’s systems were involved or who is accountable for the failure.