Bulgarian border police received a report of an explosive device on board the plane travelling from Bergamo via an email at around 10:35 local time on Tuesday (8:35 GMT), it says in a statement sent to the BBC.

The plane landed at Sofia Airport at 11:10 and was inspected by officers from the Specialised Counter-Terrorism Unit (SOBT) and the General Directorate of Border Police (GDBP) and no explosive device was found, the statement adds.

Meanwhile, it says the same email also reported "a similar threat" against a flight from Dublin, which landed at Sofia Airport at 13:35 local time.

An inspection of this plane was also carried out by officers from SOBT and GDBP assisted by four police dogs, it adds.

In a separate statement sent to the BBC, the Bulgarian Ministry of Interior says that the aircraft, passengers, crew and luggage of both flights were inspected and no explosive devices were found.

Authorities will be working together to determine if this is coordinatedpublished at 16:08 GMT

16:08 GMT

Marc Ashdown
Transport correspondent

European airspace is on high alert after this series of threats.

No explosive devices have been found, and while officially there is no link between them, the authorities from various countries will be co-operating to assess whether this was a coordinated attack, designed to disrupt airspace.

These types of threats can be made by phone or email, and can be hard to trace. But sophisticated systems and procedures ensure hoaxes are dealt with as swiftly as possible, with minimum disruption.

Passengers on board - and even the flight crew in some cases - will not necessarily be informed of the situation.

But all threats are taken seriously by airlines and airports - history shows that in the rare cases they turn out to be credible, an attack on aircraft can have devastating consequences.

What happens when a bomb threat is issued?published at 15:44 GMT

15:44 GMT

By Thomas Copeland

BBC Verify has consulted aviation safety experts about what happens on board a plane when a bomb threat is issued.

Marco Chan, a former pilot for Cathay Pacific Airways and Hong Kong Airlines who is now senior lecturer in aviation operations at Kingston University, says a bomb threat is considered “genuine until it is resolved, even though most turn out to be hoaxes”.

Chan says crews will “quietly search” toilets, galleys and storage areas and will not touch a suspicious item unless it has to be taken to an area on the aircraft designated as the “least risk bomb location”.

The aircraft’s captain will have multiple factors to assess, according to former airline pilot Terry Tozer and aviation safety commentator. These include what facilities are available at the airport they are being diverted to and how the plane could continue onward should it turn out to be a false threat.

Chan adds that once on the ground, the plane is generally “taken to an isolated stand, passengers are disembarked, and police and bomb disposal teams search it”.

Aviation security expert Paul Mason says bomb threats on passenger planes "don't happen that frequently", which makes these incidents "unusual".

"It sounds like they've been made in a credible manner across a broad range of airlines," he tells BBC 5 Live. "That would suggest to me that it's been a very deliberate act by a typical actor rather than a load of coincidental, malicious calls."

Mason explains "there are a lot of processes" that the onboard crew and people on the ground must go through "to validate the credibility of the threat".

He says in such circumstances the primary responsibility for the crew is the safety of the aircraft and "maintaining a calm state in flight is absolutely essential".

Mason adds that the aircraft may be asked to divert if the credibility of a threat "is of a certain level" and in some cases the onboard crew may not even be advised on what the ground operators are dealing with.

Image source, PA Media

A sniffer dog has been filmed inspecting a Ryanair flight in Spain following a suspected bomb threat.

A flight from Manchester to Murcia was searched by emergency services following a threat. Earlier a Spanish official explained no explosives were found on the plane and normal activity has since resumed at the airport.

A dog was seen searching around the plane as firefighters waited nearby.

The Bulgarian transport minister has said there were bomb threats against two planes travelling to Sofia, local media reports.

Georgi Peev tells the state-owned Bulgarian News Agency (BTA) that there were threats against a flight travelling from the Italian city of Bergamo to Sofia - an incident we've already reported.

He also says a threat was made against a flight travelling from Dublin to the Bulgarian capital.

That brings the total number of flights reported threatened today to seven, in addition to another plane on Monday.

Peev explains that the flights into Sofia were not diverted and no explosives were found when the planes were checked.

A Bulgarian interior ministry spokesperson told news agency AFP that the flight which landed in the Bulgarian capital, Sofia, was a Wizz Air flight from Bergamo in Italy.

Bulgarian local media earlier reported that the plane flew from Israel.

This map highlights the European airports where planes have landed following suspected bomb threats.

As a reminder:

• A flight from London Heathrow to Warsaw-Chopin Airport made an unscheduled landing at the Polish capital's other airport, Warsaw-Modlin
• Another flight, from Copenhagen to Warsaw-Chopin Airport, landed as planned before being inspected

• A Ryanair plane from Manchester to Murcia in southern Spain also faced a threat, and was inspected on landing - read a passenger's account here
• Bulgarian media reported a flight landed in the capital Sofia after a bomb threat was received by email - a Bulgarian interior ministry spokesperson told AFP the flight came from Bergamo in Italy. It was earlier reported the plane was Israeli
• Two Ryanair flights - one originating from Lisbon and one from Dublin - were searched in Rome, sources at Rome Fiumicino airport confirmed. One was escorted by the Italian military

A passenger on a flight from Manchester to Murcia says she was unaware of the suspected bomb threat until after the plane landed.

"We weren't told anything during the flight," Sarah tells BBC 5 Live. "The plane stopped quite suddenly and then we were kept on the runway for around 30 minutes."

"Then the fire engines turned up, the bomb squad turned up and we were asked to evacuate," she continues.

Sarah describes how the flight had not been on the ground a minute before it was "surrounded by fire engines and police and a bomb squad".

She explains passengers were escorted by police and made to walk from the runway to the airport, leaving all their belongings on the plane.

"We were only later told that it was an actual threat, a bomb threat to the plane itself," she adds.

Laura Gozzi
Europe reporter

Sources at Rome Fiumicino airport have confirmed to the BBC that two Ryanair flights - one originating from Lisbon and one from Dublin - were searched following anonymous tips regarding potential bomb threats.

Police bomb disposal experts carried out standard security protocols to ensure the safety of all passengers and crew.

Inspections of the passengers, luggage, and the aircraft yielded negative results, and the alert has since been cleared.

The flight from Dublin (FR9611) was escorted by the Italian Air Force until landing.

Image source, FlightRadar

Flight tracking site FlightRadar has data on the route of a Lot airline flight from London Heathrow that was forced to divert to Warsaw Modlin Airport.

The flight was heading to Warsaw Chopin airport but changed direction and instead landed at Warsaw Modlin airport at around 09:00 GMT, according to FlightRadar.

A graphic of the plane's flight path shows it took a sharp left as it reached the edge of Warsaw.

The flight then diverted to Warsaw Modlin Airport.

Some more details now on the Ryanair flight from Manchester to Murcia airport in southern Spain.

Francisco Lucas, the Spanish government's delegate in the region, says the Civil Guard has ruled out there being explosives on the plane following an inspection.

The airport is now resuming normal activity, he added in a post on X, thanking emergency teams.

Earlier, Lucas said 121 people had disembarked the plane, including crew.

The local fire service posted on Facebook this morning to say two emergency units had been sent to the airport following the threat.

Image source, Getty Images

The latest incidents come one day after a Wizz Air flight that took off from London Luton was forced to make an emergency landing in Budapest after a mid-air bomb threat.

The plane, travelling to Sofia in Bulgaria, was escorted by a Hungarian fighter jet before making the emergency landing at Budapest Liszt Ferenc International.

Authorities there "carried out the necessary security checks on the aircraft and passengers", a spokesperson for Wizz Air said.

The airline later confirmed an inspection had been "completed and nothing was found".

Hungarian defence minister Romulusz Ruszin-Szendis confirmed his country provided the fighter jet to escort the flight.

Warsaw-Modlin Airport has reopened but officials are continuing to inspect an aircraft involved in a "reported bomb threat," the airport says.

"Passengers and crew remain in the arrival halls, awaiting further action," it says in its latest statement.

The airport adds that several areas remain closed until further notice.

Two passenger planes have been inspected in Warsaw, and a third in Murcia in Spain, following a series of bomb threats.

Local media in Bulgaria say a plane flying from Israel has also landed at Sofia airport after a bomb threat was received by email.

One flight from London Heathrow made an unscheduled landing in Warsaw Modlin airport where it was inspected by specialists. It was en route to Warsaw's main airport, Chopin, with 181 people on board.

A second flight from Copenhagen to Chopin airport also faced a bomb threat, Danish media reported. It landed as normal.

Meanwhile, a Ryanair plane from Manchester made an emergency landing at Murcia airport in southern Spain, due to another threat.

That flight had 121 people on board, including crew, according to Francisco Lucas, the Spanish government's delegate in the Murcia region.

The separate incidents came the day after a Wizz Air flight from London Luton made an emergency landing in Budapest, escorted by a Hungarian fighter jet, after a bomb threat.

This is a developing story - we'll bring you more shortly.