After the surprise attack on September 11, 2001 the resolve of the US Government never to be caught unprepared again by a terror attack is entirely understandable. There is ample intelligence that al-Qa'ida is ready to mount new attacks on US cities and power plants using civilian airliners as flying bombs and the US Government has no option but to be ready if and when they come. This will likely ensure air travellers will suffer similar inconveniences to those of recent days - flights cancelled or diverted in mid flight - for years to come. It explains why the Americans are insisting sky marshals ride shotgun on international flights into the US. It accounts for the upgraded identification people entering America will require. And it makes sense of the demand that flight crews check airline toilets for suspicious packages, with an FBI report revealing terrorist plans to smuggle bomb components on board jets for in-flight assembly.

None of these measures are popular - they will make entering the US a harder and more inconvenient process. A judge in Brazil has directed that US visitors must be finger-printed, in retaliation for the American requirement for Brazilians arriving in the US. Portugal, Denmark and Sweden have refused to put sky marshals on flights to the US. But foreign complaints are not likely to sway the Americans.

For the American people, September 11 was a rerun of Pearl Harbour - an act of war. And in wartime national security takes priority. This does not mean American security standards are all beyond debate. Warnings that passengers should not queue in aircraft aisles for toilets looks foolish. The prospect of a fire-fight between sky marshals and a terrorist on a packed jumbo jet is a grim one. And travellers mistaken for terrorists arriving in the US can expect a hard time. But the memory of the twin towers burning will not quickly fade from the American mind. We might not like it, but a more suspicious welcome for travellers to the US is here to stay.