No explosives were found, despite extensive searches on the ground after the planes all took off and landed safely in different European cities just several hours apart.
Irish budget carrier Ryanair appeared to be the worst hit, with four of its flights to different destinations being targeted.
London’s Metropolitan police confirmed it “was made aware of threats … against four aircraft due to depart from or arrive at Heathrow Airport” Tuesday, one of Europe’s busiest air hubs.
It gave no further details, but also said there was a further warning about a flight at Manchester Airport.
Following checks “no security issues were identified”, the Met police added.
Two bomb warnings targeted planes heading to the Polish capital Warsaw, including an SAS Scandinavian Airlines flight from Copenhagen and one from Heathrow operated by Polish airline LOT, Polish airport authorities said.
Aena, the Spanish airport operator, confirmed an emergency protocol was activated “due to a bomb alert” on a Ryanair flight which landed at 10:30am (0930 GMT) from Manchester at Murcia in southeastern Spain. The plane arrived without problems.
Other Ryanair flights from Lisbon to Rome, Dublin to Rome, and Dublin to the Bulgarian capital of Sofia also received warnings.
Italian air force jets were scrambled to escort Ryanair flight FR9611 from Dublin as it landed at Rome-Fiumicino at 10:45am (0945 GMT), Rome Airport said in a statement.
Anti-bomb procedures were also put in place when an earlier Ryanair flight arrived at 9:40am (0840 GMT) at the airport. “Checks on passengers, luggage and the plane were all negative and the alert was lifted,” the statement added.
A Wizz Air flight from Bergamo, Italy, was inspected after landing at 0910 GMT in the Bulgarian capital Sofia following an alert, a Bulgarian interior ministry spokesperson told AFP.
The incidents all come after fighter jets were scrambled on Monday when a Wizz Air flight from London’s Luton airport to Sofia was diverted following a bomb threat and forced to make an emergency stop in Budapest.
