WASHINGTON, March 14 (Xinhuanet) -- The American aviation system remains vulnerable to attack by al Qaeda and other terrorist groups, with noncommercial planes and helicopters offering terrorists particularly tempting targets, a government report concludes.

    Intelligence indicates that al Qaeda may have discussed plans to hijack chartered planes, helicopters and other general aviationaircraft for attacks because they are less well-guarded than commercial airliners, according to a special assessment on aviation security cited by The New York Times on Monday.

    The confidential assessment was compiled by the Federal Bureau of Investigation and the Department of Homeland Security two weeksago, the Times report said. It is an effort to give a broader picture of the state of knowledge of all issues affecting aviationsecurity, officials said.

    The aviation sector has received the majority of domestic security investments since the Sept. 11 attacks, with more than 12billion dollars spent on upgrades like devices to detect explosives, armored cockpit doors, federalized air screeners and additional air marshals.

    The new assessment makes clear that counterterrorism officials still consider the aviation industry to be perhaps the prime target for another major attack because of the spectacular nature of such strikes.

    The report detailed particular vulnerabilities in what it called "the largely unregulated" area of general aviation, which includes corporate jets, private planes and other unscheduled aircraft.

    "As security measures improve at large commercial airports, terrorists may choose to rent or steal general aviation aircraft housed at small airports with little or no security," the report said.

    The report also said that al Qaeda "has apparently considered the use of helicopters as an alternative to recruiting operatives for fixed-wing aircraft operations." The maneuverability and "nonthreatening appearance" of helicopters make them attractive targets for terrorists to conduct suicide attacks on landmarks or to spray toxins below, the report said. Enditem