The United States has disclosed that it is carrying out safety inspections at airports in some of the world's major cities in an attempt to head off what is seen as the growing threat of attack from portable missiles.
Missiles narrowly missed an Israeli plane leaving Kenya last year
Concern was fuelled last November when terrorists thought to be members of al-Qaeda narrowly failed to hit an Israeli charter flight taking off from Mombasa in Kenya.
The man in charge of American military transport, General John Handy, has described the threat of such attacks as perhaps the greatest of all in the modern-day fight against global terrorism.
Overseas inspections by aviation safety investigators began several weeks ago, and are being carried out in Athens, Istanbul, Manila and several other foreign cities which feature on scheduled American airline routes.
The investigators have also been sent into airports in Baghdad and Basra, in Iraq, where the threat is deemed to be particularly high since these are just about to re-open to regular international passenger flights in the aftermath of the war.
The danger there is held to come from anti-American elements loyal to the ousted leader Saddam Hussein, who were blamed for a pair of incidents earlier this summer when shoulder-fired missiles were unsuccessfully fired at American military cargo planes.
Elsewhere, however, the threat is seen as coming primarily from the al-Qaeda network, which was behind the 11 September attacks on New York and Washington two years ago.
Cheap and available
A report by the United States Congress has calculated that as many as 700,000 of these portable surface-to-air missiles could be in circulation, at prices on the black market as low as $5,000 apiece.
General Handy recently told journalists that the missiles now constituted perhaps the greatest threat from terrorists anywhere in the world.
The current inspections are expected to result in a number of tightened security measures, including more police patrols along flight paths.
But the move that would do most to neutralise such attacks - the installation on board commercial aircraft of anti-missile systems similar to those already installed in American military planes, including Air Force One - is still some way off as governments world-wide baulk at the cost of up to $2m a plane.