January 2010: A security officer views images from the body scanner at Manchester Airport / ANDREW YATES/AFP/Getty Images

Simon Calder answers the key questions

Airline passengers heading for America can expect much stricter airport security. So what are the concerns of the US, and what will it mean for travellers?

What’s the background?

There have been several attempts by terrorists to blow up a passenger jet bound for the US, using explosive material smuggled aboard the plane. One took place in 2001, when the so-called “Shoe Bomber,” Richard Reid, attempted to blow up a Paris-Miami flight using explosives concealed in his shoes; in 2006, the “liquid bomb plot” aimed at downing transatlantic jets was uncovered, leading to the present tight restrictions on liquids in cabin baggage; and in 2009, the “underwear bomber” Umar Farouk Abdulmutallab tried to detonate a bomb aboard an Amsterdam-Detroit flight.

Intelligence has now reached Washington DC suggesting that another attempt could be made, involving much more creativity and sophistication on the part of the bomb-makers. The latest intelligence obtained by the US suggests that a bomb could be taken through airport security in a smart phone, e-book reader, laptop or tablet computer, or concealed in shoes.

Accordingly, the Homeland Security Secretary, Jeh Johnson, said: “I have directed TSA to implement enhanced security measures in the coming days at certain overseas airports with direct flights to the United States.”

What will it mean for passengers?

There should be no effect on the vast majority of travellers using UK airports, because they are travelling to other destinations – for which the security regime is unchanged.

Passengers heading for America will pass through the normal central search, but will encounter a second, more intrusive, check at the gate – shortly before they step aboard the plane. More technology is likely to be deployed in the form of swab analysis to test for microscopic evidence of explosives. Passengers can expect their shoes to be screened, and any electronic devices to be closely inspected.

The Transportation Security Administration says: “During the security examination, officers may also ask that owners power up some devices, including cell phones. Powerless devices will not be permitted on board the aircraft.”

Heathrow airport warns: “Make sure any electronic devices are charged before you travel. If your device does not switch on, you may not be allowed to bring it on to the aircraft.” Gatwick airport advises: “Make sure your hand baggage contains only valuables and items you will need during the journey.”

The problem is particularly acute for transit passengers. Suppose you are flying on the popular route from the UK via Reykjavik to the US. The first flight is three hours long, enough to deplete some laptops. If you cannot power up the computer at the Icelandic airport, it and/or you will not be allowed on board.

So I could face my phone or computer being confiscated?

On some airlines you may have a choice, of sorts. You could choose to surrender the device to security and then board the plane. Virgin Atlantic says: “Customers can leave a device with the airline at the airport but the customer will be responsible for all costs to have it returned to them. We will give the passengers a receipt which details how to get their items back and the items will be looked after by G4S who will log all items and store them for the passenger. Passengers can arrange collection on their return.”

British Airways says: “We have in place a range of options if customers are not able to comply, when requested, with the new US regulations. Customers can ask to be rebooked on to a later service. If you wish to carry on the item as part of your hand luggage, you will need to ensure that the device can be charged ahead of your rebooked flight. Customers are able to leave the device behind and hand it to a member of British Airways’ customer service team. You will be asked to complete a form and the item can be collected on your return to Heathrow or forwarded to an address of your choice.”

American Airlines told The Independent: “Customers departing from certain European airports with electronic device that won’t power on will be given the option to mail the device to their home or other location, discard the device, or be rebooked on a later flight at no charge.”

United declined to comment.

However, abandoning your device or surrendering your flight should be a last resort. If you have left the charging cable behind, other passengers may be able to lend you theirs so you get enough juice for the duration of the check.

BA adds “Please do not bring any broken devices in your hand luggage to the airport as you will not be able to fly as planned.”

Must I leave stuff out of my cabin baggage?

Unlike August 2006 – when suddenly liquids were banned – the rules on what you can carry have not changed. But if you don’t need electronic equipment on board, consider placing it in your checked baggage. In particular, if you have a broken piece of equipment that you are waiting to get fixed, make sure it goes in your checked luggage. Don’t place your chargers in your checked baggage, though, in case your device runs out of power.

What if I buy new electronic gear in an airport duty-free shop?

If you are flying to the US, you must be confident that you will be able to charge it sufficiently before going through the departure-gate check.

Is my flight likely to be disrupted?

No. There were huge queues for security at Manchester airport in the few hours following the alert becoming public. These were not caused by more intensive security at central search – but by passengers panicking and thinking, “We’ve got to get to the airport now or we’ll miss our plane.” The fears about long waits became a self-fulfilling prophecy.

Evidence from Heathrow and Gatwick, the main US gateways, suggests only minor delays. If these increase, for example because of the time taken to screen passengers at the gate, long delays or even cancellations could occur. But so far, UK airports and airlines seem to be coping.

Will it be the same when I am flying home from the US?

No. This is a specific fear about flights originating in Europe or the Middle East. Security for inbound departures to the UK remains unchanged.

Is this a permanent change that we have to get used to?

The deputy prime minister, Nick Clegg, says so – but experience suggests otherwise. Extra checks for US-bound flights were implemented in 2009 after the “underwear bomb” attempt, but were quietly withdrawn in the following months. Overall, the trajectory of airline security is moving to become less intrusive and more accommodating, e.g. allowing liquids in quantities greater than 100ml.

Ultimately the present security search area should be replaced with a long corridor equipped with detection equipment. But the US will always be a special case. This is, once again, a reflection of American concerns about the destruction of US-bound jets, rather than a global threat against all kinds of passenger aviation.

By concentrating on this particular risk, could we be missing other dangers?

Possibly. The aviation community is alarmed that the queue for security could itself become the target of a “landside” airport attack perpetrated by terrorists who have not had to go through security.

There are also concerns about hard-to-detect implanted weapons; every day, drug “mules” carry narcotics that have been placed within their bodies, and it is plausible that a suicide bomber could emulate them. Finally, there is a constant worry that a surface-to-air missile could attack a plane landing or taking off. Several unsuccessful bids have been made, and many suitable weapons are in circulation among the world’s terrorists.