The threat of portable missile system attacks will top the agenda when international aviation security experts meet in Montreal in March, International Civil Aviation Organization Council President Assad Kotaite said.

Terrorists fired two such missiles at a Boeing 757 in Kenya in November, narrowly missing the aircraft as it took off from Mombasa airport with Israeli tourists returning to Tel Aviv.

The attack "raised concerns worldwide in the civil aviation community that this type of terrorist attack may spread to other regions and target carriers from other nations," Kotaite said.

He spoke at the opening of the three-day World Civil Aviation Chief Executives Forum in Singapore.

Preliminary figures for 2002 show airline traffic worldwide rose 2 percent from the previous year and after a sharp slowdown following the Sept. 11, 2001 attacks, Kotaite said. But total traffic remains 2 percent to 3 percent lower than levels in 2000, he said.

Singapore Transport Minister Yeo Cheow Tong said the Kenya attack "increased the level of apprehension" and showed the world that terrorists tactics "will evolve and take new forms."

An estimated 27 guerrilla and terrorist groups worldwide have Soviet SA-series shoulder-fired missile launchers, which now outnumber the U.S.-made Stinger missiles that spread through Afghanistan in the 1990s, according to Jane's Intelligence Review.

The weapons can last up to 22 years and are nearly impossible to track until they are used because groups buy them on the black market, the defense journal said.

Al-Qaida reportedly has a number of the missile launchers, which if true, means Osama bin Laden's organization "represents the most significant threat to international civil aviation," Jane's wrote following the Kenya attacks.