A controlled explosion was carried out at 5.15pm after an estimated 2,000 people were ordered to evacuate the terminal following the discovery in the security search area at about 2pm.
More than 50 flights were cancelled and 13 were diverted to other airports. Full services did not resume until 10pm.
“We are working hard throughout the night and into tomorrow morning [Tuesday] when we expect operations to return to normal,” the airport said.
Police said the item was destroyed and “although deemed suspicious, did not present a wider danger”.
EasyJet, which diverted six flights to Stansted, Birmingham and Southend, cancelled the rest of its flights to and from Luton for the day. Services were due to return to normal this morning.
The airline said it had cancelled 41 flights as a result of the disruption.
The airport had said: “We understand passengers will be frustrated by the delays they are experiencing.
“We are working closely with the police to ensure passengers are not inconvenienced unnecessarily but we must ensure that the safety and security of all our passengers and staff remains our top priority.”
Sourced from Travel Weekly