AMSTERDAM: It was once the nightmare of air travelers the world over: a passenger jet parked in a remote corner of an airport surrounded by armed police and ambulances.
The frightening scene that played out this past week at Amsterdam's Schiphol Airport turned out to be a false alarm. But it revived memories of an aviation era when hijackings were more common than in the post-9/11 world of ultra-tight security checks at airport gates, air marshals on flights and reinforced cockpit doors.
Figures compiled by the International Civil Aviation Organization show seven "unlawful seizures" of planes in 2001, the year of the Al-Qaeda attacks on the United States. The highest number in any year since was five in 2009. The group recorded no airliner seizures in 2010 or 2011.
Despite the drop, authorities are far from complacent and attempted attacks continue - the group showed acts including sabotage attempts rising from just two in 2005 to 14 in 2009 before dropping off sharply to three in 2011.
Jim Marriott, chief of the organization's Aviation Security Branch, said the group is organizing a high-level conference next week aimed at further boosting security.
"The prevention of hijackings and other acts of unlawful interference with civil aviation is of utmost importance," he said.
Philip Baum, editor of Aviation Security International, said the current security measures are a strong deterrent.
"People feel that the powers that be are very security conscious and are looking out for people," he said.
Many existing security measures were introduced or strengthened in the aftermath of Sept. 11, 2001, when al-Qaida militants hijacked four commercial jets in the United States.
Armed only with box cutters, the terrorists seized control of the planes, slamming them into the twin towers of New York's World Trade Center and the Pentagon in Washington. The fourth plane plowed into a field in Pennsylvania after passengers and crew members fought back against the hijackers. In all, the attacks killed nearly 3,000 people and forever changed the way we fly.
If anything, Wednesday's false alarm only served to underscore the lengths to which authorities now go to prevent 9/11-style attacks. Before the recent London Olympics, the British military posted anti-aircraft missiles capable of shooting down a hijacked jet on top of an apartment block and at five other locations.
Shortly after Dutch air traffic controllers lost contact with the pilots of Spanish carrier Vueling's Airbus A320, two F16 fighter jets were scrambled and flashed over the pancake-flat landscape, setting off a sonic boom as they broke the sound barrier on their way to intercept the plane and make visual contact with its pilots to make sure nothing was wrong.
Police in the Netherlands have completed an investigation into the incident, but no details have been released into exactly what happened.
Col. Peter Tankink from the Volkel air base where the F16s are based told The AP such alerts are a fairly regular occurrence: The jets are scrambled about 15 times a year, he said.
It is possible Wednesday's false alarm got far more publicity simply because many media crews already were at Schiphol to report on the discovery earlier in the day of a World War II bomb during excavation work.
Analysts say that even with beefed-up security, deranged individuals continue to pose a threat to airliners and terrorists are still trying to bring them down.
That has been shown several times since 9/11, with the most notable cases being those of "shoe bomber" Richard Reid in 2001 and "underwear bomber" Umar Farouk Abdulmutallab in late 2009. Both men unsuccessfully tried to blow trans-Atlantic flights out of the sky using elaborately concealed explosives.
And just two months ago, a group of men allegedly tried to take control of a plane in China's far-western Xinjiang by battering the cockpit door with a crutch and trying to set off explosives. Overseas activists denied it was a hijacking by Uighur rebels and said the incident was no more than a fight over seating.
One of the most bizarre hijacking attempts since 9/11 was in Australia in 2003, when a passenger smuggled wooden stakes onto a flight and stabbed cabin crew as he attempted to seize control of a domestic flight.
The would-be hijacker, David Mark Robinson, said he wanted to crash the Qantas jet "to rid the world of the devil." He was later found innocent on grounds of mental impairment and ordered held in a secure psychiatric hospital.
It appears that not just post-9/11 security is at play. Analysts who have studied hijackings say the phenomenon was already on the decrease well before 9/11.
Harro Ranter, a Dutchman who compiles a list of hijackings from official sources and media reports, says many hijackings in the 1960s and early 1970s - the most prolific era for taking over aircraft - were by people trying to escape from or get to communist regimes.
"When the Soviet Union fell apart, that led to a decline in attempted hijackings," he said.
Baum said organizations responsible for hijackings in the 1970s and '80s also may have given up on the tactic simply because it did not appear to further their political aims.
"The real change wasn't post-9/11, it was post-1980s and I think the real major change was the fact that none of these major hijackings was ever particularly successful," Baum said. "Palestine never became independent as a result of hijackings. If anything, it turned the world against their cause."
But Baum warned that terrorists are likely already plotting ways of beating current airline security and predicted they could even try surgically implanting explosives in the body of a suicide bomber to beat airport scanners.
He said airports should be using scanners capable of recording what was in passengers' bodies, not just objects concealed in or under their clothes.
"(Existing) body scanners are a major improvement on metal detection," he said. "But realistically we're buying into the wrong type of scanners."