India, Nov. 7 -- As flight delays continued at New Delhi's Indira Gandhi International Airport (IGIA), an information technology (IT) ministry official said that the disruptions were not due to a cyber attack.

The official, who did not wish to be named, said a technical glitch in the course of upgrading the Air Traffic Control (ATC) software caused the delays. "There is supposed to be an automatic updation of flight plans, which stopped functioning. It is not a cyber attack," said the official.

People aware of the matter said the IT ministry checked on Friday morning to rule out a cyber attack. The civil aviation ministry authoritatively informed it that it was not, they added.

The IGIA is the country's busiest airport, handling over 1...