More than 200 flights were delayed at Delhi airport, one of the world's busiest, after an air traffic control messaging system suffered a technical problem, India's airport authority and a source familiar with the matter said on Friday.

The glitch, which delayed departures for dozens of flights by more than 30 minutes, could cascade and lead to logjams at other airports in the country.

Shares of IndiGo were down 1.5% after the airline said its flight operations were affected. SpiceJet and Air India also warned of delays.

The Airports Authority of India said a technical issue in the Automatic Message Switching System, which is used to generate flight plans, forced controllers to develop them manually, leading to delays.

The problem with the system started on Thursday evening local time, the source said.

"Technical teams are working to restore the system at the earliest," AAI said in a post on X. The agency did not respond to additional requests for comment on what caused the malfunction.

Broadcaster CNN NEWS 18 reported that authorities were investigating if computer malware could be a cause.

The incident follows a ransomware attack that disrupted some of Europe's biggest airports, knocking out automated check-in systems and affecting flights in September.

The glitch delayed about 25 flight departures on Thursday and more than 175 on Friday at Delhi airport, the source said. Delhi airport handles 60-70 aircraft movements per hour. Data from Flightradar24 showed the average departure delay was 55 minutes.

The malfunction also hit several international airlines, with an ITA Airways flight to Rome delayed by nearly two hours and a Virgin Atlantic flight to London by more than an hour. Flights scheduled to take off between 6 a.m. and 8 a.m. (0030 GMT and 0230 GMT) were the most affected.

Aircraft were still landing at the airport, but take-offs were disrupted, an airline source told Reuters. Air Traffic Control has not yet told airlines when the issue would be resolved, the source added.

Delhi airport handled about 78 million passengers in 2024, making it the ninth busiest airport in the world, according to Airports Council International. The operator of the airport is majority owned by GMR Airports, while air traffic control is managed by the AAI.