Plane off runway in turn for take-off

A Singapore Airlines flight with 187 passengers on board veered off the main runway while turning for take-off at Calcutta airport around midnight on Monday, leaving its nose wheel stuck on the ground.

The Singapore-bound Airbus A330 remained stuck off the runway for nearly two hours until early on Tuesday.

The aircraft had to be brought back onto the tarmac with a tow bar fixed to a tug, a small vehicle with a powerful engine that is used to push a plane on a parking bay.

Two passengers, one of them a pregnant woman who became unwell, opted out of the flight before it finally took off around 4am.

"Singapore Airlines flight SQ517 from Calcutta to Singapore on November 7, 2016, experienced a delay of nearly four hours. This was due to the repositioning of the aircraft at the runway for take-off, and a further delay as a passenger was unwell and needed to disembark.... The airline apologises for the delay and inconvenience caused," a spokesperson for the carrier said.

The directorate general of civil aviation (DGCA) has instituted an inquiry into the incident.

A senior airport official said getting the Airbus A330 back on the runway was a difficult task with the nose wheel getting stuck in a lump of earth. "The aircraft is heavy and since the wheel wouldn't budge, it was a difficult procedure."

Since the runway surface was dry, the possibility of the aircraft skidding was negligible.

A senior pilot with an international airline said there could be several reasons for an aircraft moving out of the runway while turning for the final run ahead of take-off.

"It could be a pilot's failure to properly manoeuvre the aircraft. There could also be a problem with the runway centreline lights that help the captain maintain alignment. Taxiway markers can become less conspicuous or it could be a problem with the surface," the veteran pilot said.

Airport officials said all scheduled flights between midnight on Monday and around 4am on Tuesday operated out of the secondary runway because of the incident on the main runway.