On 22 March 2016, 32 people were killed and at least 200 injured by suicide bombings at Brussels Zaventem international airport in Brussels. On 28 June 2016 a combination shooting and bombing attack on Atatürk Airport, Istanbul, left 45 dead. The destruction of a Metrojet airliner above the Sinai desert on 31 October 2015 by an on-board explosive device was the most devastating airborne terrorist attack since 9/11. These recent atrocities, committed by ISIS, re-state aviation as a perennial prime target for terrorists.

Countermeasures are often brought in as a response to intelligence or a recent method used to attack an airport or aircraft. In mid-2014, overseas passengers were told to power up electronic devices on US-bound flights – based on intelligence that al Qaeda bomb-maker Ibrahim al-Asiri had developed a new type of explosive to blow up aircraft. He had earlier constructed the ‘underpants bomber’ device smuggled on board a US-bound aircraft on Christmas Day 2009 – which led to the enhanced installation of whole body scanners in airports to spot concealed devices.

Technologies for detection

A specific ongoing challenge is detection of homemade explosives such as TATP, liquid explosives, and chemical detonators. A combination of technologies along with sniffer dogs can gain a complete picture of a hidden device. But no method is foolproof. The security operative must be able to spot anomalies in both passengers and their luggage; therefore, proper training of security staff is vital while they are under constant pressure to keep millions of passengers moving.

X-ray is used worldwide as the main explosives detection system (EDS) to ‘see inside’ a device in luggage. Smiths Detection provides the full range of airport scanners, including the HI-SCAN 6040aTiX and HI-SCAN 6040-2is HR with multi or dual view, high resolution imaging for carry-on bags. The Smiths HI-SCAN 10080 XCT, based on dual-energy, dual-view X-ray technology and computed tomography, can screen up to 1,800 bags per hour.

For detection of traces of explosives, security personnel collect residues with swipe wands; the swipes are heated to vaporise the explosives, and the vapours analysed in a tabletop detector. Current detectors – ‘sniffers’ – typically use ion mobility mass spectrometry to recognise specific ionized chemicals, based on their chemical properties. The Bruker DE-tector operates via a large touch screen and is the first Explosive Trace Detection (ETD) instrument designed and built in Europe with a non-radioactive source that achieved the European Civil Aviation Conference (ECAC) Certification for passenger and cargo. The Bruker RoadRunner is a dual mode handheld system both for vapour traces and for swab sampling, making it well suited to cargo screening.

Whole body scanners use millimetre waves, which lie in the spectral region between radio waves and infrared. This band can pass transparently through lightweight materials such as clothing fabrics on the traveller and provides an animated image of a suspect object. Body scanners are controversial on grounds of privacy and effectiveness; however, they offer an added layer of deterrence.

Spotting anomalies

To spot and stop a suicide bomber in the land-side area in the terminal is far more difficult. Following the Brussels attack, authorities in New York, London, Paris and Frankfurt increased police numbers at airports, and in South Korea, Japan, Indonesia, Thailand and India checks on passengers entering terminals were increased, with additional patrols inside terminal buildings.

This follows some elements of the Israeli model – a series of concentric circles with increasing scrutiny closer to the aircraft. At Ben Gurion Airport all vehicles that arrive must first pass through a preliminary security checkpoint where armed guards search the vehicle and speak to the driver and occupants to gauge their mood and intentions. Plain-clothes officers (and robots) patrol the area outside the terminal building, with hidden surveillance cameras operating 24/7. Armed security personnel patrol the terminal and keep a close eye on people entering the terminal building.

Security personnel will approach suspect individuals and engage them in conversation to gauge their intentions and mood. Vehicles are subject to a weight sensor, a trunk x-ray and an undercarriage scan. From arrival to departure, the passenger can go through 12 layers of security.

Departing passengers are questioned by security agents before they reach the check-in counter, for from one minute to an hour, based on such factors as age, race, religion and destination. The agents look for nervous or inconsistent statements. Around 5% are singled out for additional screening, which can involve hours of questioning. All digital photos owned by a traveller could be examined and body searches are customary. Luggage is taken apart one item at a time. However, this approach is said not to work for larger, busier airports. In 2015 ‘only’ 16.5 million passengers used Ben Gurion while 75 million passed through Heathrow and 66 million through Paris Charles de Gaulle.

Countermeasures are meant to ensure a degree of passenger safety and security – but often have to be tempered with passenger convenience in an era of increased air travel. Some believe that more rigorous passenger checking at the terminal entrance would enhance congestion and provide even more targets. And technology isn’t the only fruit: spotting the ‘presence of the abnormal’ is paramount.