The bomb scare arose at a time when security is at an all-time high in view of the Republic Day celebrations on Tuesday across the country and especially in Delhi.
This is the second incident in the last two days as on Saturday a GoAir flight from Bhubaneshwar for Mumbai was diverted to Nagpur for similar reasons.
The bomb threat call was received at the airport terminal just before the scheduled departure of the Kathmandu-bound Jet Airways flight 9W 260 at 1.25 pm, officials said.
Officials said the plane has been taken to the isolation bay at the IGIA and all passengers de-boarded for a thorough anti-sabotage check.
The bomb threat assessment committee has been activated, they said, and a final clearance for the flight is awaited.
Jet Airways, later in a statement, said that its Kathamandu flight from here has been delayed due to a security alert.
All 104 guests and seven crew have been disembarked from the aircraft and taken to the departures waiting area at the Delhi airport, the airline said in a statement adding security agencies are conducting a search of the aircraft.
"We apologise for the inconvenience caused to our guests. Security of our guests and crew is always our number one priority," Jet Airways said in the statement.
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