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.
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 10:30 am (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.
A Panama-flagged cruiseship, meanwhile, was evacuated late Tuesday in the island of Syros following a bomb threat, the Greek coastguard said.
The Crown Iris was anchored there and bound for Haifa in Israel with around 1,500 passengers and crew on board. No explosive device was found and the ship was due to resume its journey, they said.
Jets scrambled
Italian air force jets were earlier scrambled to escort Ryanair flight FR9611 from Dublin as it landed at Rome-Fiumicino at 10:45 am (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 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.
Scandinavian Airlines said it could “confirm that a threat has been made against flight SK751 between Copenhagen and Warsaw” but the plane landed Tuesday without any problem.
It arrived at Warsaw’s Chopin airport, which closed one runway as the plane underwent a security inspection, but no explosives were found.
The LOT flight, which had also been scheduled to arrive at Chopin, was diverted to the Polish capital’s other airport, Warsaw Modlin.
Authorities closed that airport following the alert, but the Boeing 737 MAX also landed safely. “Nothing was found,” Modlin airport spokesman Adam Szablowski told AFP.
Hungarian Defence Minister Romulusz Ruszin-Szendi said on Facebook that on Monday NATO’s air defence alert service had issued an alert for a Wizz Air flight from London’s Luton.
“The Hungarian Defence Forces’ Gripen fighter jets took to the air within minutes and ensured the safe landing of the passenger aircraft in Budapest,” he said.
