While the government said passengers would now be permitted to carry a single bag onto planes, authorities at London Heathrow and other major airports said the ban on carry-on luggage would continue for another day.
The severe security rules imposed on Thursday had led to congestion and wholesale cancellation of flights from Heathrow, Europe's busiest airport. The critical level was declared last week as police rounded up 23 people suspected of involvement in a plot to detonate bombs on U.S.-bound aircraft.
BAA PLC, which owns Heathrow and other major airports, said that passengers would be allowed to carry on one small bag effective Tuesday morning, but that a strict ban on carry-on luggage remained in effect Monday.
Home Secretary John Reid said the downgrading of the threat level reflected intelligence indicating that a terrorist attack was not imminent, and was not in response to problems at airports, according to the AP.
The Department of Transport announced new rules which restrict the size of the carry-on bag to a maximum length of 45 centimeters, width of 35 cm and depth of 16 c.
No liquids of any type are permitted through the airport security search point, other than prescription medicines in liquid form essential for the flight, and baby milk and liquid baby food which must be tasted by the accompanying passenger in the presence of security officers.