The US has sought stricter security at foreign airports with direct flights to America in view of intelligence reports of al Qaeda planning strikes using bombs that escape security checks.
It was not clear which of the around 250 foreign airports with direct connections to the US would be affected. The UK said it had stepped up security at its airports.
“I have directed TSA to implement enhanced security measures in the coming days at certain overseas airports with direct flights to the United States,” said secretary for homeland security Jeh Johnson in a statement on Wednesday.
“We are sharing recent and relevant information with our foreign allies and are consulting the aviation industry.”
American intelligence has picked up information that al Qaeda bomb-makers have moved to Syria and tied up with its affiliate there to make a bomb that can escape detection, said Associated Press citing an unidentified counter-terrorism official.
Al Qaeda has been at it for a while.
Richard Reid, a British man, tried to set off an explosion on a Paris-to-Miami flight in December 2001 using explosives concealed in the sole of his shoes.
Umar Farouk Abdulmutallab, a Nigerian, tried to explode explosives stitched into his underwear on a flight from Amsterdam to Detroit in December 2009.
They both failed, but in both instances they had managed to smuggle the explosives on board without being detected. Taking off shoes has since Reid become a part of the security drill.
There are apprehensions that many Americans and westerners now fighting with al Qaeda and other insurgents in Syria or even Iraq could be used for these strikes.
Anyone with a western passport would probably not be subjected to the same strict scrutiny, enabling them to smuggle in explosives easily, without detection.