A quartet of jackals that first looked like dogs from the cockpit of an aircraft readying for takeoff forced two other planes to hover above Calcutta airport for an extra 15 minutes and burn fuel worth about Rs 63,000 each.

An IndiGo Airlines Airbus 320 that was arriving from Nagpur and a smaller Kingfisher aircraft from Agartala were the ones to be affected. Either of the airlines could have suffered more than just monetary loss had the pilots of a Deccan flight to Patna not spotted the four-legged intruders while taxiing for take-off.

Air Traffic Control was informed about it at 5.55pm. “The captain reported that there were four dogs on the runway. They were later found to be jackals,” an official said.

When airport personnel were clearing the runway, the Nagpur-Calcutta flight was only four nautical miles away and the Kingfisher plane at a distance of 12 nautical miles from the landing strip.

“It is not just the cost, but the bigger issue of safety during takeoff or landing that worries us. It is clear that the airport authorities have no respect for rules meant to ensure safety on the runway,” an official of one of the private airlines said.

Dogs and jackals have free access to the two runways and taxi bays after dark. The 19 people employed to keep the runway clear of birds and animals go off duty after dusk.

On March 27, a Kingfisher Airlines aircraft ran into a dog on the runway of Bangalore airport during take-off, causing the nose landing gear to collapse. The crew evacuated the 25 passengers on board after the aircraft screeched to a halt.