MUMBAI, Oct 4: Air traffic control officials in Mumbai said on Thursday they were investigating a power failure that left them unable to direct planes over India’s financial capital for several minutes.

The incident on Wednesday morning saw controllers at Mumbai’s airport biting their nails as electricity was cut and battery back-up devices failed to kick in.

Around 20 flights were in the air at the time of the black-out, although no accidents or delays were caused by the incident.

“Power went off for 3-4 minutes. The UPS (uninterruptible power supply) failed to come on immediately,” an air traffic control official said.

According to the Indian Express, the generators and back-up systems were unplugged for maintenance, while the one functioning UPS tripped because it was overloaded.

This left only one emergency radio frequency operational, although the paper said it was quickly jammed “as all aircraft tried to seek instructions through this communication channel.” India’s Directorate General of Civil Aviation (DGCA) has sought an explanation from Air Traffic Control.

“We are doing an internal assessment of what went wrong. We will also file our report with the DGCA, as mandated,” the ATC official said.—AFP