The US Department of Homeland Security on Sunday scaled back the threat level for commercial airline flights from Britain to the United States from Red to Orange, or High.
The downgrading came after British authorities changed the United Kingdom's terrorism threat level from Critical, meaning an attack is expected imminently, to Severe, meaning an attack is highly likely, the DHS said in a statement.
The DHS last week raised the US threat level to Red, or Severe for US-bound flights originating in the United Kingdom after British authorities announced they had foiled a plot to blow up multiple flights heading to the United States.
Britain has arrested about two dozen people in connection with the plot.
Homeland Security Secretary Michael Chertoff said cutting the US threat level did not mean the threat had passed.
"We are remaining vigilant for any signs of planning within the US or directed at Americans," Chertoff said in a statement. "We are maintaining a heightened level of security for United Kingdom flights bound for the United States and have put in place added measures for these flights," he said.
He said the United States and the United Kingdom were now essentially at parallel security levels in aviation.
The DHS statement said the US threat level remained at Orange for all domestic and all other international flights and that a ban on liquids and gels in carry-on baggage remained in effect.