Aircraft are a magnet for extremists. By bombing a plane, militants can kill many people at once in a headline-grabbing manner, gaining maximum publicity for their cause. So it is no surprise that, despite a spate of measures taken since the terror attacks in the US on September 11, 2001, extremists keep trying to attack passenger aircraft. And every time they do, authorities tack on yet more security measures. A Nigerian man's attempt to detonate a bomb on a transatlantic flight on Christmas Day has predictably been met with new rules further inconveniencing people flying to the US. But more restrictions will at most inconvenience terrorists who will find the next loophole to exploit; safer skies are best ensured with better intelligence and on-ground protection. The Nigerian, Umar Farouk Abdulmutallab, had explosives moulded to his body and sewn into his underwear. Security checks in Nigeria and Amsterdam failed to detect them. His attempt to detonate the bomb was foiled not by the crew, who are trained for such eventualities, but fellow passengers. Warnings of his extremist views made known to American officials were not translated into his name being added to airport watch lists. Toughened rules as a result of the incident mean that people flying to the US can now take only one small piece of hand luggage into the cabin of a plane. They will not be able to leave their seats an hour before the flight lands and cannot keep items on their laps. A series of bombing plots uncovered since September 11 mean that passengers on international flights the world over can take no more than 100 millilitres of liquid on board and are subjected to an array of security checks that require arriving hours early for flights. Flying is an integral part of the global economy, but the plethora of checks and requirements make for inconvenience, time-wasting and stress. Quick-witted passengers, not security rules and regulations, stopped the suspect from carrying out this latest plot. He would not have come so close to succeeding had there been greater alertness to the threat he posed. Technology may one day make detecting the bomb he was carrying possible, but extremists will always be trying to beat innovation. Foil-proof airport security may never be possible - so intelligence and information-sharing are likely to remain the most reliable prevention.