Security is to be tightened at US airports following an incident at Glasgow airport and a bomb alert in London, the White House has said.
Airports across the US will see alert-raising measures
Spokesman Tony Snow said there was no indication of a specific threat to the US, and no change to the country's overall security level.
But he said the security presence at airports would be reinforced for the sake of vigilance.
Travellers are being told the measures could cause some delays.
On Saturday, a blazing car was driven into the main terminal building at Glasgow Airport.
It came a day after two cars were found containing explosives in central London.
Mr Snow said the Transportation Security Administration (TSA) would carry out some "alert-raising measures" at airports across the US.
"You are likely to see those in the increased presence of some TSA agents outside terminals, there will be some inconvenience to passengers in terms of longer wait times," he said.
"It's important to know that we remain committed to being vigilant throughout the country, including at airports."