India, Nov. 8 -- 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.

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.

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 do...