An Aer Lingus pilot is under investigation after he allegedly refused to land during a bomb threat on his flight.

Several bomb threats were made against airlines on Thursday — the second incident this week after several other flights were diverted and grounded after further bomb threats.

One of the flights on Thursday, an Aer Lingus flight that departed Dublin bound for Rome, had to land at the Évreux Air Base, just north of Paris, after it was circling French airspace for a period of time.

It has now emerged that French authorities have begun an investigation into the pilot after he allegedly refused to land at the military base.

It is alleged that the pilot wanted to land at a civilian airport instead of the military base, but eventually landed at the military base. No explosives were on board the plane.

Aer Lingus said in a statement on Thursday night that they ‘fully co-operated with the French authorities regarding this matter, and the engagement of pilots with the authorities has now concluded.’

The latest round of bomb threats comes just days after a number of flights were diverted for the same reasons.

The Aer Lingus flight was bound for Rome but diverted to a major military base in Evreux, France, after the bomb alert.

French publication Le Figaro reported that a French Rafale fighter jet escorted the plane on approach.

French Prime Minister Sébastien Lecornu confirmed that 151 passengers and six crew members were on board and are all safe.

The Guardian reports that two of the planes came from Copenhagen and Madrid, respectively. Both landed in Sofia, while the third came from London Stansted and was diverted to Plovdiv.

A fourth flight, from LOT Polish Airlines, has also been threatened. The flight departed Warsaw on Thursday and was set to arrive at Brussels Airport. It has since landed in Zaventem.