Editor's note, Oct. 29, 2010:False alarms of possible improvised explosive devices on cargo aircraft in the United Kingdom and the United States emphasize critical security vulnerabilities in the global air cargo shipping system. This is an issue STRATFOR has been tracking for years, and this analysis from 2005 details some of the technical aspects of this security challenge. For breaking coverage of this incident, please visit our situation reports section. A Government Accounting Office (GAO) report released Nov. 16 concludes that serious vulnerabilities remain in the U.S. air cargo system. Unless steps are taken to address the security issues contained in the report, terrorists could easily exploit these vulnerabilities. In 2004, approximately 6 billion pounds of cargo were shipped by air aboard passenger aircraft in the United States. This cargo is stowed in the belly of the aircraft along with passengers' luggage. An explosive device smuggled into the cargo hold could result in the destruction of the aircraft in the air — and kill hundreds of people. When an airliner is at high altitude, pressure is maintained in the fuselage similar to that at ground level. Because the pressure outside the aircraft is much lower than inside, a small breach in the aircraft's exterior can cause explosive decompression, and result in disintegration of the aircraft. Traveling at altitudes higher than 30,000 feet and speeds faster than 500 mph, few can be expected to survive. That is what happened Dec. 21, 1988. Pan Am Flight 103, a Boeing 747, broke apart over the town of Lockerbie, Scotland, after 12 to 16 ounces of plastic explosives concealed in a Toshiba tape player inside a checked bag were detonated in the plane's forward cargo hold. Evidence suggests that the aircraft disintegrated instantly, and that it was caused by a hole less than 2 feet wide in the 747's 225-foot fuselage. The bombing killed 270 people, including 11 on the ground. Placing explosives in cargo as a way to attack aircraft is not a new concept for terrorists. In 1995, terrorist mastermind Abdel Basit, aka Ramzi Yousef, planned to plant a bomb disguised as cargo in the hold of a U.S.-flagged airliner from Bangkok, Thailand, as part of Operation Bojinka, a plot to blow up several airliners over the Pacific Ocean. Yousef's plan failed when his co-conspirator, Istaique Parker, got cold feet. Parker, a South African Muslim who had been living in Pakistan, had been assigned the task of placing the bomb on the aircraft as cargo. Instead of carrying out the assignment, however, he gave Yousef a bogus excuse about needing an exporter's license that would require a photograph and fingerprints to ship items to the United States. Yousef and Parker returned to Pakistan where, motivated by greed, Parker turned Yousef in for the reward money, and U.S. agents then moved in for the arrest. Had Yousef not been arrested, there is very little question that he eventually would have set his plan in motion. Since the Pan Am bombing 17 years ago, various government studies have pointed out vulnerabilities in the air cargo system. Measures were studied to "harden" aircraft cargo containers — to make them strong enough to withstand small explosions — but were determined to be too expensive, and the hardened cargo containers too heavy. To discourage another Pan Am 103 or Operation Bojinka, airlines can verify if someone checks a bag but does not board the plane, and all checked baggage is now inspected by Transportation Security Administration (TSA) agents. Current measures regarding cargo transported on passenger flights, however, are inadequate. U.S. Reps. Edward Markey and Christopher Shays from the House Homeland Security Committee ordered the GAO report, and have criticized the TSA's current measures. According to Markey, although 100 percent of passengers are checked before boarding an airliner, many large cargo items are not — giving travelers a false sense of security and overlooking a major potential gap in security. Both Markey and Shays have introduced bills that would require air cargo screening, while the Department of Homeland Security, which oversees the TSA, agrees with the GAO findings and recommendations. The Democratic Markey and Republican Shays have made this a bipartisan issue — pointing out a very real vulnerability and urging action. It remains to be seen whether adequate measures to inspect cargo transported on passenger flights can be put in place before the vulnerabilities in the system are exploited.