Airport security is being increased at British airports after the United States called for heightened precautions amid reports two terror networks are working together on a bomb that could evade existing measures.
The Department for Transport said the extra measures - which have not been disclosed - were not expected to cause "significant disruption" to passengers and noted that the official UK threat status remained unchanged,
Changes were announced after Washington Homeland Security Secretary Jeh Johnson ordered beefed up security at foreign airports from where aircraft fly directly to the US.
"The UK Government keeps aviation security under constant review in conjunction with international partners and the aviation industry," a DfT spokesman said.
"We have taken the decision to step up some of our aviation security measures. For obvious reasons we will not be commenting in detail on those changes.
"The majority of passengers should not experience significant disruption. There will be no change to the threat level, which remains at substantial.
"The safety and security of the public is our paramount concern. The UK has some of the most robust aviation security measures and we will continue to take all the steps necessary to ensure that public safety is maintained."
US officials were reported to have said the move was the result of intelligence that groups in Yemen and Syria had joined forces to plot an attack.
Prime Minister David Cameron's official spokesman said: "There are terror organisations around the world that seek to do the UK, its citizens, citizens of many other countries including our Western allies, harm.
"We need to always be vigilant to situations that can develop."
Speaking on ITV's Good Morning Britain, Deputy Prime Minister Nick Clegg said he hoped disruption at airport security would be minimal.
He said: "It's very important that we work - as we do - with our American partners and indeed with other countries around the world so that where credible new threats are identified a response is then implemented in airports around the world.
"We will play our part as will other countries to make sure where security checks can be tightened up, they will be.
"The hope is that the majority of travellers will not be unduly disrupted but I hope also that people will understand that we have to work together across the world to deal with people who want to inflict harm."
Asked what had prompted the latest move, Transport Secretary Patrick McLoughlin replied: "We constantly keep the whole issue of aviation under constant review along with our international partners and also the aviation industry and obviously we have acted on advice and information that we have received."
He went on: "I would like to reassure the travelling public that we have one of the toughest security regimes in the world, along with the US.
"It's very important that we take these measures to protect the travelling public and to ensure the travelling public have confidence that when we get information, we take the right measures and hopefully those right measures will reassure the public in their travels."
Asked about delays to passengers, Mr McLoughlin replied: "I hope it won't delay them that much. There have to be extra checks made but those will be made in the course of events going through the security that people already go through, which are fairly stringent as it is.
"I hope there will not be significant delays. Obviously we will work with the airports to try and make sure that that is not the case, so that people who are going on business or going away on holiday get away on time."
The tightening of security came as a message was posted on a Twitter page purporting to be that of a British jihadi in Iraq, saying the UK was "afraid" he might come back with skills he had learned fighting with terror group the Islamic State in Iraq and Greater Syria (Isis).
The message was posted yesterday on an account believed to belong to Nasser Muthana, from Cardiff, who appeared in an Isis propaganda video released last week.
He tweeted, alongside a picture of containers: "So the UK is afraid I come back with the skills I've gained."