The FAA has given airlines until 9 April 2003 to make permanent upgrades to the cockpit doors of their aircraft, saying it will impose these requirements on foreign aircraft flying into the US. About 4,000 US airliners have been given temporary upgrades, which will be mandatory for all airliners in the US by 25 February. One problem is to provide a way for the flight attendants to get into the cockpit in an emergency that incapacitates the pilots without making it possible for terrorists to force the attendants to let them into the cockpit.--Stephen V Cole