For the third day.. “bomb threats” hit air traffic in Europe.. What do we know?

(CNN) -- Air traffic in Europe was affected, on Friday, for the third day in a row, by false reports of the presence of bombs. This led to the disruption of more than 20 flights across the continent, and in certain cases prompted some countries to send fighter aircraft.

More than a dozen flights were affected Thursday, including the rerouting of four flights in the Czech Republic and two flights in Italy.

Police in both Denmark and the Czech Republic reported on Friday that new threats were directed at air traffic at Copenhagen and Prague airports, respectively. The police forces in both countries sought to reduce the extent of the threat to the public. The Danish police assessed that there was no risk to passengers, while the Czech police stated that they had "taken the necessary security measures, with minimal impact on the usual operations at the airport."

On Tuesday, at least seven flights and one cruise ship received bomb threats.

This is what we know so far:

How were the threats made?

It's not entirely clear, although Czech and Italian authorities say it was sent via email.

A representative of Vaclav Havel Airport in Prague told CNN that the threats the airport received regarding the presence of bombs on board four flights were received via an anonymous email.

A Czech police spokesman told CNN that the email was addressed to the airport, adding that similar messages were sent to other airports in Europe.

The threats regarding flights in Italy were received in an email sent by an anti-feminist group calling itself “Male State” to a logistics company with Fiumicino Airport in Rome.

An email, first reported by CNN affiliate SkyTG24, included a false claim that there were “explosive devices” on two flights — one from Helsinki and the other from Dublin. An airport spokesperson confirmed to CNN the authenticity of the screenshot.

The International Counter-Terrorism Center, a research center based in the Netherlands, stated that the “Male State” movement was founded in Russia in 2016 as an anti-women movement, and later emerged as an explicit supporter of the war in Ukraine. In 2021, a Russian court banned this movement and classified it as an extremist organization.

All European airports are developing plans to deal with incidents of this type and conducting training on them. Speaking to CNN, Keith Jeffries, former director of federal security at Los Angeles International Airport (LAX), explained that all airports “have bomb threat management plans and conduct training based on those plans,” allowing them to make decisions within seconds.

The bottom line, Jefferies said, is that no aviation authority would ever ignore a bomb threat.

Who is behind it?

Again, it remains unclear at this point who exactly is behind these threats. No European country has yet identified any specific party or country behind it. For its part, the European Union stated that it is too early to say whether these incidents are related to each other.

Security analysts indicated that it may be part of a broader hybrid campaign or a series of malicious hoaxes.

Eric Schouten, head of the aviation security group Diame, indicated that saboteurs working for the Russian state may be responsible for this.

“From railways to food infrastructure - including hacking of refrigeration systems and other such operations - it is all consistent with the approach of Russian state actors seeking to destabilize Europe,” Schouten said, according to Reuters. He also pointed out that many of the affected countries had provided support to Ukraine in its war against Russia.

The German Foreign Ministry also pointed to the Russian invasion of Ukraine, saying that Europe's security was "being tested far beyond the front line in Ukraine." The Ministry cited bomb threats, cyber attacks targeting refrigerators in major stores, and drones that penetrated the airspace of some European countries as examples of these threats.

The UK Transport Secretary described the threats as a "malicious hoax".

In statements to British media, Heidi Alexander said that the flight disruptions had triggered “established procedures to deal with false reports and malicious threats, which is exactly what these threats represent.”

What is the effect?

In general, the impact remained relatively limited. So far, all the threats have proven to be false, with the relevant authorities reporting that no explosive devices were found.

These things, of course, caused disruption to travellers' journeys. On Thursday, passengers and crews on board at least 14 planes were affected; An Aer Lingus flight heading to Rome was diverted to France, and two flights coming from Spain and Denmark were forced to change their course towards Sofia, the capital of Bulgaria. This comes after at least seven flights were rerouted on Tuesday.

Analysts warn that the threats may be aimed at causing disruption, while also monitoring the response of airlines and authorities.

“These aviation threats coincide with cyberattacks targeting refrigeration systems in supermarkets across Europe,” Iliran Almog, CEO of Cyviation, a company specializing in aviation cybersecurity, told Reuters.

He added: "Various basic services are experiencing disruptions that entail economic costs and undermine public confidence."