France today boosted passenger screening at its airports, responding to a Washington request for extra security for US-bound flights over fears Islamist radicals could be plotting new attacks using hard-to-detect bombs.
The French move, announced by the DGAC civil aviation authority, follows similar action by Britain, and notably impacts Europe's two busiest hubs: Heathrow and Charles de Gaulle.
Combined, an average 2.5 million passengers use those two airports each day.
French and British authorities urged passengers to allow extra time to get past the additional measures, which were not specified but were believed to focus on footwear and electronic items such as mobile phones and computers.
US officials on Wednesday publicly demanded enhanced security for airports in Europe and the Middle East which have direct US flights. They did not say whether they had intelligence about a specific plot, but their actions suggested alarm.
The request was "based on real-time intelligence," according to a Homeland Security Department official who spoke on condition of anonymity.
Yesterday, the US embassy in Uganda warned of a possible plot targeting Entebbe airport serving the capital Kampala for later that day. But the danger period elapsed without incident.
Western intelligence services are concerned that hundreds of Islamist radicals travelling from Europe to fight in the Middle East could pose a security risk on their return. Most European passport-holders do not need a visa to travel to the United States.
One of the radical organisations, Al-Qaeda in the Arabian Peninsula (AQAP), is of particular concern.
US and other intelligence services believe AQAP is passing on sophisticated bombmaking expertise to militants fighting in Syria for use against Western targets -- most prominently, passenger aircraft.
"We have a long-standing concern of terrorist groups in trying to get undetected material on the planes," a US intelligence official said.
AQAP "is always the group we think about when we talk about undetectable bombs," the official added.
Brooke Rogers of the War Studies Department at King's College London said that for extremist groups, bringing down an aircraft was the "ultimate prize -- if the attackers succeed, it will be spectacular for them".
And "unfortunately in aviation, it doesn't take a big amount (of explosives) to make a boom," said US airplane security expert Jeff Price.
France's aviation authorities said in a statement its new security measures "will be carried out in a way to limit as much as possible inconvenience to passengers, however delays are possible".
The stepped-up screening is taking place at Charles de Gaulle airport -- which has 47 US-bound flights a day at this time of the year -- and other airports in mainland France, as well as in far-flung French territories such as Tahiti.
