Media playback is unsupported on your device Media caption Holidaymakers returning from Sharm el-Sheikh say they were given little or poor information about when they would be brought home to the UK

Airport security will have to be reviewed in areas where Islamic State militants are active if the air crash in Egypt is found to have been caused by a bomb, the foreign secretary says.

Philip Hammond said increased security could mean extra costs and delays.

Some 5,300 people have returned to the UK since flights from Egypt resumed on Friday.

Mr Hammond said British tourists could face delays of "two or three days" to get back to the UK.

All 224 people on the board the Russian Metrojet flight from Sharm el-Sheikh to St Petersburg died when it came down in Sinai on 31 October. Most of the victims were Russian.

The US and the UK have both said intelligence points to the strong possibility the crash was caused by a bomb - militants affiliated to so-called Islamic State, also known as Isil, have claimed responsibility.

Security experts

Mr Hammond was asked about the implications for airport security in the Middle East, North Africa and Turkey on The Andrew Marr Show.

He said: "If this turns out to be a device planted by an Isil operative, or by somebody inspired by Isil, then clearly we will have to look again at the level of security we expect to see in airports in areas where Isil is active.

Media playback is unsupported on your device Media caption "At most people will experience a delay of two or three days" - Philip Hammond

"What we have to do is ensure that airport security everywhere is at its best and that it reflects local conditions. One of the key issues about keeping airports safe is the training, management and motivation of staff."

"That may mean additional costs, it may mean additional delays at airports as people check in."

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Analysis

Image copyright EPA

By Andy Moore, BBC News

In theory, airport security around the world is supposed to be regulated according to agreed standards by the International Civil Aviation Organization. In practice, many airports such as Sharm el-Sheik fall short.

The Israeli airline El Al has always imposed its own security-vetting procedures at overseas airports, over and above whatever is done locally.

Passengers are asked to check in at least three hours before any flight. El Al is the only commercial airline to fit its planes with missile defence systems.

The UK is moving towards a similar system by sending its own security experts to Sharm el-Sheik airport.

If security is to be beefed up in any country where so-called Islamic State operates - that will be a tall order.

It will be expensive for airlines and time-consuming for passengers - but it may well be necessary.

How has airport security changed?

Mr Hammond said reports that a British passenger plane had to take evasive action over Sharm el-Sheikh earlier this year to avoid a missile were a "red herring".

He said: "There was an Egyptian military exercise going on on the ground and I was satisfied at the end of that investigation that that was not an attempt on the plane. The plane was not in danger at any time."

Global security expert Philip Baum, editor of Aviation Security International, told The Observer that security needed to become both more unpredictable and more thorough to confound future terrorism attempts.

Mr Hammond said a team of security experts from the UK's Department for Transport was travelling continually through airports reviewing safety practices.

The costs of extending holidays for those left in the Red Sea resort, now about 14,000 people, is expected to be covered by tour operators and airlines.

Image copyright AP Image caption Russian tourists arrive from Hurghada at Domodedovo airport in Moscow, Saturday

Russia has banned all flights to Egypt but is allowing special flights to bring Russian tourists back home from Sharm el-Sheikh. Some 11,000 tourists have now been returned back to Russia.

Britons are being allowed to travel home with hand baggage only; hold luggage is to be flown back separately in the next week.

They are being urged to stay in their resorts until they are told they have a confirmed place on a flight, and to follow airline guidance about what time to arrive at the airport.

People returning to the UK have continued to describe chaotic scenes at Sharm el-Sheikh airport.

The government said almost 2,000 people had been flown back to the UK on Sunday aboard eight flights.

For Monday, British Airways has confirmed it will run one flight to Gatwick, Monarch will have two flights to Gatwick and Luton, Thomas Cook two flights to Gatwick and Manchester, and Easyjet one to Luton.