Many travellers' plans will be disrupted in the coming days or weeks, so what are your rights if you are going on holiday or taking a flight?
I don't want to fly right now, but I bought a cheap ticket with lots of restrictions. Is there is any chance that I could still move my flight?
Some companies are being sympathetic to their customers' fears - and even to those in the cheap seats.
It will all depend on who you have booked with, so you will need to check with your airline - policies vary.
Lufthansa, British Airways and Virgin are among the airlines offering customers alternative routes - and not just for flights to the Middle East.
Long haul economy customers of British Airways, for example, buying tickets in the UK between 14 February and 31 March can change their ticket free of charge, including restricted tickets - but they have to rebook their flight before 31 May and fly before the end of the year.
Customers of Virgin Atlantic who have tickets to America, Hong Kong, Shanghai, Delhi and Tokyo can change their ticket to later in the year.
"Even if you have a non-refundable non-changeable ticket you can change the date you want to travel on," a spokesman told BBC News Online.
Is this typical?
Tour operators and airlines normally take a dim view of people who simply change their mind because of nerves.
But policies differ according to how close your holiday destination is to the conflict.
If you are booked on a spring break to the Canaries, for example, but no longer want to go because you are concerned about flying, you are unlikely to get a refund.
Even if you are flying to unaffected destinations in the Middle East or Islamic countries, such as Morocco, you may have trouble getting your money back or booking an alternative without incurring a fee.
Whether the firm will step in and agree to change your flight is normally governed by how the Foreign & Commonwealth Office (FCO) views safety in that particular country.
There are some exceptions to this general rule, though.
Tour operator Lunn Poly, within its "Change your mind: change your holiday" scheme, is allowing some customers to change their holidays regardless of the level of threat.
If my flight is cancelled by the airline because of the war or the threat of war can I get my money back?
Check with the company concerned, but you are unlikely to get your money back.
Instead, the firm will most likely offer you an alternative route, or a later flight.
If you paid with a credit card, bought direct, and your ticket cost more than £100 you will be able to lodge a claim with your credit card company.
This is because under Section 75 of the Consumer Credit Act, the credit card company is jointly liable.
This extends to travel services, according to an Office of Fair Trading spokesman.
What if I'm on holiday and war breaks out?
If the country is deemed unsafe by the FCO, your tour operator has a "duty of care" to return you to the UK.
If you are an independent traveller, it will be up to the goodwill of your airline.
Any costs that are not met by the tour operator or airline, however, are unlikely to be covered by your travel insurance.
Most have exclusions for war or terrorism.
Contact the local British Consul or Embassy for help if you get into trouble and need assistance.
You can always log onto the FCO's website to check for updates. The website also contains a list of embassies and consulates around the world.
I've booked a charter holiday in the region - will my travel insurance pay if I don't want to fly?
Travel insurance will not cover "disinclination to travel" and most have exclusions for acts of "war or terrorism".
However, if the Foreign and Commonwealth Office (FCO) deems your destination unsafe, tour operators and airlines will normally step in and offer alternatives.
Will airplanes be re-routed?
According to the International Air Transport Association (IATA), the 150 flights between Europe and Southeast Asia will most likely "not experience any noticeable change" in journey times as they are normally routed "well north of the conflict zone".
Travellers in the Persian Gulf area, however, could experience up to one hour or more added flight time when re-routed, the group said on Wednesday.
Any other rights?
Last year, most UK airports committed themselves to "The Voluntary Commitments on Air Passenger Rights".
The charter contains a set of standards to improve passenger treatment and their rights.
Those who have signed up to the charter have agreed to provide passenger information on legal rights, and assistance during delays or disruption.
A number of airlines, such as British Airways, British Midland, Cyprus Airways, Iberia Airways, Kenya and Thai Airways have recently signed agreements with the Office of Fair Trading which give their customers much better rights if they are delayed or miss their connecting flight.
Under the new terms, air travellers on non-refundable tickets could be entitled to a "credit note" to cover the cost of a missed flight, due to unusual or unforeseeable circumstances.
In another change, ticket purchasers should be informed of a flight time change as "soon as possible" - and given new rights to a refund if there has been a significant change in the flight time, and the airline is unable to book an acceptable alternative flight.
Where can I find out whether it is safe to travel to a particular country?
The first port of call for up-to-date travel advice is the FCO.
Advice can be obtained by calling 0870 6060290 or through the department's website.
BBC Ceefax p 470 and the government's UK Online portal also carries the latest warnings.
Where can I go to get more information about my rights?
The Air Transport Users Council (AUC) can investigate complaints and queries from passengers on scheduled flights.
Its address is: CAA House, 45-59 Kingsway, London WC2B 6TE. Telephone 020 7240 7071.
As for problems with charter flights, tour operators are the first port of call with complaints.
However, if the operator is a member of Abta, unhappy passengers can contact that organisation. The Abta helpline is 020 7307 2043.