An electrician accidentally unplugged the radar system at the Indian capital's airport, forcing air traffic controllers to manually guide in aircraft, media reports said on Saturday.
Electricians fixing a fault accidentally unplugged the main power source of the radar late on Friday, causing radar screens to go blank, said the Times of India newspaper and other media.
Operations were shifted to manual control to assist the planes in air and for those lined up for a take-off, the media said quoting officials. No incidents were reported.
"Though the standby power took over the system within seconds, it took over 45 minutes to reboot all consoles and restore the operations fully," officials told India's NDTV network.
In 2011, a five-hour electricity blackout at the airport's newly inaugurated terminal affected scores of domestic and international flights.
The Delhi airport is hailed as an example of India's ability to build state-of-the-art infrastructure projects.