Nuclear power stations are on heightened security
Security has been stepped up at Britain's airports and nuclear power stations and there are 1,000 more officers on duty in London in the wake of the 11 September attacks.
The Metropolitan Police says there is no intelligence to suggest there is a specific threat to the UK.
And the Department for Transport, Local Government and Regions (DTRL) said security concerns in the United States did not necessarily reflect those of the UK.
The DTLR said it raised the level of security "according to the perceived level of threat", without saying what the perceived level of threat to Britain was.
Nuclear precautions
Immediately after the terror attacks on New York and Washington, the Civil Aviation Authority (CAA), at the request of the government, imposed flight restrictions over central London.
Commercial flights were diverted around the area until 16 September and there was no private flying for 24 hours.
Part of the United States' increased security - announced on Wednesday - includes a week-long ban on any aircraft movements within 20 kilometres of more than 80 nuclear plants.
Aircraft can only pass over these sites at altitudes above 5,500 metres, which means commercial flights should not be affected.
The seven UK nuclear power stations run by British Nuclear Fuels (BNFL) are already within restricted flight zones regulated by the CAA.
The zones - requested by the installations to avoid the possibility of a private aircraft needing to make an emergency landing nearby - vary from 2.8km to 3.7km in radius and up to about 762 metres.
A CAA spokeswoman told BBC News Online there had been no requests from the government to extend the areas since 11 September.
Reinforced cockpits
BNFL spokeswoman Jean Watson said its power stations were on increased security since 11 September, in accordance with government advice.
"But we feel that there is no reason to believe our facilities are under threat," she told BBC News Online.
"We work with the government and follow their rules."
She said it would not be prudent to discuss the details of the security arrangements.
The CAA spokeswoman said the authority had allowed UK commercial airlines to make modifications to cockpit doors of aircraft if they wished.
No compromise
British Airways and Virgin Atlantic have taken the initiative and are fitting reinforced cockpit doors in all their aircraft, to protect the planes from any attempt to storm the flight deck.
Passengers will also have noticed increased security at airports.
Extra armed police are on duty, there are additional searches and a list of items such as knifes are banned from hand luggage.
A BAA Heathrow Airport spokeswoman told BBC News Online measures had caused some delays at first but things were back to normal.
"Most feedback from passengers has been very positive and people prefer to take slightly longer to be processed rather than compromise security," she said.