A plane departing from Tel Aviv and heading to Vienna made an emergency landing in Sofia, Bulgaria, due to a bomb threat. At the moment, the flight operated by Austrian Airlines with around 50 people on board has reached the Bulgarian airport without damage or injuries among passengers, while all the necessary investigations are being carried out. At the moment there does not appear to be any evidence of the presence of an explosive device on board and no confirmation has been received of the discovery of a bomb, nor of the actual reliability of the threat.
In any case, when an aircraft receives or suspects a bomb threat, an internationally established chain of rigorous actions is activated. ICAO (the International Civil Aviation Organization) defines “bomb threat” (i.e. bomb threat) as a communication, anonymous or otherwise, that suggests or implies (truly or falsely) that the safety of an aircraft in flight or on the ground may be in danger from an explosive or other device.
Regardless of the apparent credibility of the threat, every report is treated as real and triggers protocols involving crew, air traffic controllers, law enforcement and airport managers. The objective is always twofold: to guarantee the safety of those on board and to protect people and infrastructure on the ground.
ICAO procedures in the event of a bomb threat on an airplane
The regulatory bases were established by ICAO through the annexes to the Chicago Convention. More in detail, each aircraft operator has the obligation to keep on board a checklist of the procedures to be followed for the search for an explosive device in the event of suspected sabotage, accompanied by indications on the behavior to be followed in the event that a suspicious object is found and by information on the “least risk bomb location” (the least risky position on the plane where a possible bomb can be located): generally, it is the point on the fuselage designed by the manufacturer to minimize structural damage in the event of detonation.
From an operational point of view, however, the FAA (Federal Aviation Administration, the US agency that regulates civil aviation) has defined detailed procedures for the management of bomb alerts which constitute a reference widely adopted even outside the United States. In more detail:
- When receiving information, from any source, that a bomb has been placed on, in, or near an aircraft with the purpose of damaging or destroying it, personnel must immediately notify the operational supervisor and, if the threat is directed at a specific aircraft with which they are in contact, inform the pilot and report the event to air traffic control centers.
- A crucial step concerns pressurization: the pilot must be asked whether he wishes to ascend or descend to an altitude that equals or reduces the pressure differential between the cabin and the external environment, since equalizing this pressure is a key step in minimizing the destructive potential of a bomb.
- The FAA also clarifies that the air traffic control center must under no circumstances provide advice to the crew on how to handle an explosive device: in the event that technical guidance is needed, information on the type of aircraft and the location of the device is forwarded to explosives experts, who make recommendations directly to the pilot.
The rules for Europe followed Tel Aviv-Vienna flight
The Austrian Airlines flight departing from Tel Aviv and heading to Vienna received a bomb threat once it crossed Romanian airspace. In Europe the procedures are defined by EU Regulation 923/2012, known as SERA, directly applicable in all member states, including Italy. The rules establish that an aircraft subjected to unlawful interference must set the transponder to code 7500 and communicate to air traffic managers any significant circumstances and any deviations from the flight plan, so as to allow controllers to prioritize the flight and reduce conflicts with other aircraft. The pilot-in-command must attempt to land at the nearest suitable airport as soon as possible, unless the situation on board dictates otherwise.
In the event that the threat indicates that a device has been placed on board an aircraft, air traffic managers must communicate directly to inform the crew of the threat and the surrounding circumstances. The aircraft must be handled as quickly as possible, while ensuring the safety of other aircraft and that personnel and ground installations are not exposed to risk. Crew requests to ascend or descend to equalize the pressure differential must be approved as soon as possible, exactly as required by the FAA.
In the event that the pilot is unable to contact air traffic services, the guidelines require him to continue flying on his assigned route and cruise level, at least until he enters radar or ADS-B coverage, and attempt to transmit warnings on the emergency VHF frequency. A further caution concerns radio communications: controllers must not make verbal reference to the illicit interference (the bomb threat, in fact), unless the pilot does so first, as this could attract the attention of a possible hijacker with potentially negative consequences.
The procedure on the ground: the role of airports
Once you reach the airport, airport procedures come into play. A grounded aircraft must remain as far as possible from other aircraft and infrastructure and, if appropriate, clear the runway to reach a designated isolated parking position according to local instructions. If the crew decides to disembark passengers and personnel immediately, other aircraft, vehicles and employees must be kept at a safe distance. FAA regulations further specify that other aircraft must remain at least 300 feet away from the suspect aircraft when possible.
Every European airport is required to prepare an emergency plan. In Italy, Airport Emergency Plans include a chapter dedicated to sabotage, bomb threat to a structure or aircraft, hijacking and seizure, drawn up in accordance with the guidelines of EU Regulation 139/2014.
A concrete case illustrates the effectiveness of this chain: in September 2014, after an anonymous phone call reporting a bomb on a Ryanair flight headed to Bergamo, the anti-terrorism plan was activated, coordinated by the Border Police with the involvement of ENAC, ENAV and the airport manager, and with the use of bomb squad, anti-explosive dog teams and firefighters. The aircraft landed regularly and reached a remote parking area at a safe distance from the airport; the passengers were subjected to additional x-ray tests before being released. The alarm turned out to be unfounded, but the episode confirmed the readiness and effectiveness of the intervention chain when every link, from the control tower to the police, operates according to the established procedures.
