The pilot and co-pilot of an Aer Lingus flight that was forced to land at a French airbase on Thursday following a false bomb threat have been allowed to leave after questioning, authorities have said.

French investigators said they spoke to the men on Thursday after being told that the aircraft’s pilot had initially refused to comply with a request to land at the Évreux base.

‘This is happening in the Europe of now,’ says Eric Schouten, head of aviation security group Dyami, following disruption to several flights over bomb hoaxes.

“Investigations are still ongoing,” Rémi Coutin, public prosecutor for Évreux, told The Irish Times.

“The pilot and co-pilot have been authorised to leave French territory following their interviews yesterday.”

In a statement, Coutin said the investigation began after the prosecutor was “informed that the pilot of the aircraft had initially refused to comply with the French authorities’ request to land at Évreux, and that two fighter jets had to be dispatched to compel him to do so”.

It aims to establish whether the request to land was refused and “whether this behaviour was likely to constitute one or more criminal offences”, the statement added.

Two French fighter jets were deployed to escort the Aer Lingus flight to land at Évreux following the bomb threat. The flight had departed from Dublin on Thursday morning and was bound for Rome.

A copy of the bomb threat sent to Italian airports, published by news agency Ansa, stated that an explosive had been placed aboard the flight from Dublin and another from Helsinki as an attack against the “feminist regime”.

[ Irish passenger describes ‘terrifying’ incident as bomb threats affect almost 30 flightsOpens in new window ]

Passengers were disembarked from the aircraft at Évreux and their baggage was searched. No explosives were found.

The Aer Lingus pilot is an Irish national and the co-pilot is a British national, according to the Évreux prosecutor.

The aircraft’s black box is to be examined as part of the investigation.

In a statement on Friday, Aer Lingus said: “The captain and crew on Aer Lingus flight EI402 acted impeccably and were thoroughly professional throughout yesterday’s security issue.

“Safety and the care of our passengers is Aer Lingus’ top priority and this was upheld professionally by the captain and crew of the aircraft throughout in what were very challenging circumstances.”

The Irish Airline Pilots Association (Ialpa) said the questioning of Flight EI402’s pilots was generally standard procedure following such incidents in French airspace.

In a statement it said the pilots cooperated fully and were being represented in France by Ialpa’s sister union, the SNPL.

“Ialpa is fully satisfied that the pilots discharged their legal and safety responsibilities to the fullest extent and acted professionally throughout,” said union president Captain Daniel Langan.

He said that in the case of an Irish-registered aircraft, legal responsibilities and powers are governed by applicable Irish law as well as the relevant laws of the state in which the aircraft is operating.

Langan said Ialpa was “satisfied that their actions were consistent with their professional obligations and their overriding responsibility for aviation safety.”

“Ialpa will continue to liaise with the relevant parties to ensure that the pilots are fully supported and can return home safely today.”

Inquiries are continuing after almost 30 flights across Europe were disrupted by hoax bomb threats on Thursday.

Officials across Europe reported more bomb threats against multiple flights on Friday.

No suspicious items were found and no one was injured, but the threats have raised concern because they came as Europe digests a host of other recent disruptions — including attacks on supermarket refrigeration systems and drone incursions.

Minister for Foreign Affairs Helen McEntee said the events, which come a week before more than 50 European leaders gather in Dublin for major summits, were “extremely concerning”.

French prime minister Sebastien Lecornu’s office said on Friday that “four new bomb threats were made today against aircraft flying over French territory”.

The planes landed safely and bomb disposal experts were conducting inspections.

A flight from Prague to Bucharest operated by Romanian carrier Tarom received a bomb threat. The plane landed at its intended destination, and airport administration officials said the bomb threat proved to be false.

Portuguese police said they were informed of a bomb threat targeting a Ryanair flight travelling from Lisbon to Rome, and carried out a security inspection once the aircraft landed in Lisbon. Passengers and luggage scheduled to travel to Rome underwent additional security screening before boarding.

Police in Venice said a WizzAir flight from Prague to Rome was diverted to the Italian city after a bomb alert. Passengers were evacuated after the aircraft landed, and authorities were carrying out security checks. The inspections had so far produced negative results, according to police.

Air traffic at the airport was temporarily suspended but resumed.

Meanwhile, police in Denmark and the Czech Republic both said they investigated threats to air traffic.

In the Danish capital, Copenhagen, police said on Friday they went to the airport for a second consecutive day “in connection with threats directed at air traffic” as a precautionary measure. They said they assessed that there had been no danger to passengers or to others at the airport, and that air traffic was proceeding safely and without disruption.

Czech police also said they were again dealing with threats against arriving and departing planes on Friday. They said necessary security measures were taken in co-operation with Prague’s Vaclav Havel Airport that had “a minimal impact on the normal operations at the airport”.

Fake bomb threats are relatively common but it is unusual to see so many in such a short period. – Additional reporting: Reuters