– Air France's fourth bomb hoax since the Nov. 13 attacks on Paris led to the detention of a former police officer Monday, the first arrest since a spate of scares began disrupting travel for thousands of its passengers.

French authorities said a retired French police officer was held after Air France Flight 463 completed its journey from the Indian Ocean island of Mauritius following a diversion to Kenya early Sunday prompted by the discovery of what turned out to be a fake device left in one of the Boeing 777 jetliner's lavatories.

The retired police officer traveling on Flight 463 was freed Monday after nearly 12 hours of questioning.

The incident on an aircraft that was carrying 473 passengers and crew follows a series of anonymous telephone calls that led to the diversion of three Air France flights departing the United States for Paris over the past 4½ weeks. In those cases, nothing untoward was found following searches on the ground.

While bomb hoaxes — whether from disgruntled clients or for more malevolent reasons — have long afflicted airlines, such a proliferation is unparalleled in recent times and wasn't directed at a single carrier even after the Sept. 11, 2001, attacks on the U.S.

The loss of 224 lives on a Russian Metrojet plane in a suspected bombing by ISIL terrorists on Oct. 31 has made authorities especially jittery, with the Islamic State in Iraq and the Levant also claiming it was behind the Paris atrocities.

"Security remains the top priority," the airline said in a statement when asked how it was responding to the incidents, reiterating comments Sunday from Frederic Gagey, who heads up the unit of Air France-KLM Group.

Europe's biggest airline said on Dec. 8 that last month's Paris attacks, which claimed the lives of 130 victims, had wiped out about $54 million of revenue in the last few weeks of November alone and that it could be May before its pipeline of forward bookings returns to normal.

Five days after the assaults, Air France flights from Los Angeles and Washington to the carrier's Charles de Gaulle hub made unscheduled landings in Salt Lake City and Halifax, Nova Scotia, respectively, following phone threats called in to a reservation center at Delta Air Lines, the European carrier's U.S. partner in the SkyTeam alliance.

The FBI attended the plane diverted to Salt Lake and Canadian police assisted by sniffer dogs searched the aircraft in Halifax, where the main runway was closed. An Air France service from San Francisco to Paris was grounded in ­Montreal earlier this month after another call. Authorities are scrutinizing phone records in relation to all three incidents.

Following the discovery on the Mauritius flight, members of the 777's crew were also interrogated by police after the landing in Paris, while a court in Bobigny, outside the city, has begun an investigation after Air France filed a complaint.

Aircraft diversions can be particularly disruptive — and costly — for airlines, since passengers may need to be put up in hotels or have their journeys rebooked, while planes are left out of position for subsequent flights, upsetting planned timetables.

Gagey said no evidence has been found to suggest that security procedures failed. Photographs of the fake bomb, which didn't contain explosives, appear to show that it was made of cardboard and featured a timer, he said.

The company said it doesn't know who prepared the package and how it got into the aircraft restroom. Security measures have been stepped in Mauritius as a precaution.

Overwhelmed with relief, the passengers arrived safely in Paris on Monday, some crying as they embraced loved ones.

"We thought we were going to die. Because of the speed of the airplane going down, we thought we would crash in the sea," said passenger Marine Gorlier after landing at Charles de Gaulle Airport.