British authorities arrested two more suspects July 2 in connection with what appears to have been an attempted suicide attack at the international airport in Glasgow, Scotland
, on June 30 as well as the discovery of two crude vehicle-borne improvised incendiary devices in central London the day before. Although seven suspects — likely including the two main actors responsible for all three attempts — are now in custody following the amateurish
plot, the threat of other attacks remains. The similar construction and lack of complexity of all three devices strongly suggests they were made by the same person or people, none a trained bombmaker. Because British authorities have said the London and the Glasgow cases are linked, then, it is quite likely the two arrested at the scene of the Glasgow attack also planted the vehicles containing firebombs in London. The devices used in both cities were incendiary, made from canisters of propane with gasoline as a catalyst. In both London incidents, the mechanisms for remotely initiating the devices failed to function. In Glasgow, the attackers appear to have tried to ignite the device manually rather than remotely, possibly because they could not devise an effective remote method — as evidenced by the failures in London. Also, given the intense manhunt in the wake of the London attacks, the perpetrators might have believed they were about to be caught and decided to launch one final attack in an effort to become martyrs. The shift in deployment suggests the two men were learning by experience, though their capture will eliminate their chance to improve further on their design for a vehicle-borne improvised explosive device (IED). The devices were incendiary, not explosive, meaning they were capable of causing intense flames, but little concussive force. Though a firebomb can be dangerous to people and damaging to structures in the immediate vicinity, it is less likely to damage buildings or cause casualties than a blast caused by high explosives. Although gasoline vapors can cause a powerful explosion, it is difficult to create a viable improvised fuel-air explosive device. Nevertheless, it appears as though the attackers expected the device in Glasgow to explode — and it did not. They did manage to get the vehicle as far as a terminal building, though the device failed to function as they had hoped. Because propane tanks were also used in these attempts, some media sources have suggested the devices were similar to those employed by Iraqi insurgents
. While propane is sometimes used in IEDs in Iraq, the devices deployed in the United Kingdom have little in common with Iraq's powerful car bombs, which always involve the use of high explosives. The use of gasoline rather than high explosives to ignite the propane also suggests that the plotters had little experience in designing effective IEDs. The cell appears to have had little practical knowledge, and no skilled bombmaker. Despite their misguided efforts, however, it is clear the bombers intended to cause massive damage and casualties. The bombers likely had no access to explosives or the precursors needed to make improvised explosives such as TATP, which suicide bombers used against London's transportation system July 7, 2005. As a result of the long struggle with Irish Republican Army bombers and the 2005 London bombings, British authorities tightly control
the sale of precursor chemicals that can be used to manufacture improvised explosives, and require that nitrogen in fertilizers be diluted. These measures, combined with stepped-up vigilance and public consciousness regarding bulk sales of acetone and peroxide — two ingredients in TATP — might have frustrated the latest attackers' efforts to acquire such materials. In addition to the two suspects arrested on site following the Glasgow attempt — the likely perpetrators of the London attempts as well — five other people have been arrested in connection with the attempts in London
and Scotland. On June 30, a doctor reportedly of Jordanian-Palestinian origin and his wife were arrested on the M6 motorway near Glasgow. A day later, a 26-year-old man was arrested in Liverpool in connection with the London and Glasgow incidents, and two other men were arrested later in the Paisley area west of Glasgow.
Additionally, British authorities have searched at least 19 locations in connection with the attempts, including a rented house near the Glasgow airport, where they believe the two suspects in that attack lived. Searches of homes also were conducted in southern Liverpool and in Newcastle-under-Lyme in Staffordshire in the Midlands. Documents, phone numbers, addresses and the contents of computers found at the house searched near Glasgow could help lead security officials to any other cell members still at large, or could reveal potential plans for other attacks. Interviews of the detained suspects likewise could shed light on the cell, its motivations, capabilities and future plans. Given the amount of information being gathered, the high level of vigilance, and the fact that other plans might have been compromised by the arrests and searches, any cell members still at large stand a good chance of being apprehended before they can carry out further attacks. Even if the cell responsible for the London and Glasgow attempts is completely rolled up, however, the United Kingdom will remain on alert. The plot failed miserably, but it nevertheless could inspire copycats
, as did the 2005 London bombings.