Bomb threats disrupt flights across Europe for the second time. Here’s what we know

Flights across Europe were targeted by "hoax" bomb threats on Thursday for the second time this week, disrupting air travel across London, Dublin, and Helsinki, among others.

At least 27 different flights were impacted, according to Reuters, with some forced to land unexpectedly and others escorted by fighter jets.

Aer Lingus, Finnair , Wizz Air and Polish airline LOT confirmed to CNBC that some of their flights were affected.

It comes after seven passenger planes across Europe, two departing from the U.K., were targeted by suspected bomb threats on Tuesday and were described as "malicious hoax threats" by the U.K. government.

Finnair said two of its flights — one from Helsinki to Rome with 144 passengers and 7 crew members and another from Helsinki to Vienna with 177 passengers and six crew members — received "unfounded or hoax" bomb threats on Thursday, with both flights landing safely and customers disembarking the aircraft.

Local authorities in Rome and Vienna inspected the two flights and didn't find anything out of the ordinary.

"Unfortunately, air traffic is sometimes subject to threats, as we have seen this week, when other airlines in Europe have also faced hoax bomb threats," Finnair said in a statement. "Threats are almost always unfounded."

Hungarian budget carrier Wizz Air confirmed to CNBC that its flight from Milan's Malpensa Airport to Bucharest's Otopeni Airport, as well as another flight to Warsaw, were subject to bomb threats on Thursday.

The flight to Bucharest was approaching its final destination and landed safely when the threat was reported at Otopeni, with security checks subsequently clearing the aircraft. Wizz Air's Warsaw flight was diverted.

"This incident comes amid a series of similar bomb threats affecting several airlines across Europe in recent days," Wizz Air told CNBC. "Wizz Air is not the only airline targeted, with other carriers also experiencing threats resulting in flight diversions and security checks."

Irish airline Aer Lingus diverted its Dublin to Rome flight to Normandy on Thursday morning, while Polish airline LOT said two of its flights from Warsaw received security threats. Both were cleared following security inspections, the airlines told CNBC.

Air France's CEO Ben Smith said none of its flights were affected, but the coordinated threats are unprecedented. "It's unfortunate, and we hope it won't give consumers any reason to slow down or reduce their travel plans."

U.S. Transport Secretary Sean Duffy told CNBC's "Squawk Box" on Thursday that the incidents appeared to be "false attacks."

He added: "We take safety very seriously, which is why, if you see any issue in the airspace or threats in the airspace, we shut it down...and so, with all of our assets in the U.S. government and our partners over in Europe, we are tracking this together and working together to make sure the American airspace, the American traveler, is safe."