The U.S. Congress, stunned by the sky-high cost and problematic performance of missile defense systems for commercial airliners, has ordered the Department of Homeland Security to look for cheaper ground-based defenses, the latest issue of Defense News reported.

The department has spent more than 100 million U.S. dollars since 2003 studying whether it makes sense to put missile defenses on commercial airliners, a project that was partially prompted by an incident in November 2002, when terrorists fired two missiles at an Israeli airliner taking off from Mombasa, Kenya.

Both the missiles missed the target, but the incident demonstrated that airliners are vulnerable to small man-portable missiles.

The department was paying two major defense companies, Northrop Grumman and Raytheon, to develop detailed plans for missile defense systems that would sit at airports to protect planes as they arrive and depart, as high cost makes its almost impractical to install missile defense systems on airliners themselves.

Raytheon was proposing a ground-based missile defense system that uses microwaves to scramble the homing devices in shoulder- fired missiles, causing them to veer off course and miss their targets. The system would cost about 25 million dollars per airport, Alan Fischer, a Raytheon spokesman, was quoted as saying.

Northrop Grumman offered a similar price - 25 million to 30 million dollars - for its Skyguard missile defense system, which would use high-powered laser to shoot down missiles fire at airliners, the report said, citing company spokesman Bob Bishop.

Homeland Security Department officials were pressing companies to design missile defenses that cost no more than 1 million dollars per airliner, but even with that price, equipping the country's 6,800 commercial airliners would cost 6.8 billion dollars.

The purchase price was only part of the cost, as maintenance fees could also be very high. Ground-based defenses would be far cheaper, defense experts said.

Editor: Yan