Hester Lacey buys a cheap flight

ANSWER A SMALL ad for a cheap flight, or drop into a bucket shop, and once you could have expected to be told that the pounds 50 return to New York is only available on the third Wednesday in the month, leaving at 4am, and to qualify you have to be aged under 25, with long red hair, and be prepared to wear a purple shell-suit throughout the flight. Oh, and they only had two of those tickets to start with anyway, and they've both just been sold. But how about this other, more convenient, but more expensive ticket?

Today, however, cheap flights such as the British Airways World Offers promotions are plentiful - and they really do exist. "Availability is good," says a spokeswoman for discount specialists STA Travel. "These are not the sort of fares that seem dodgy because they are so cheap and when you phone you find they are an afternoon fare available one day a month. The British Airways ones are certainly genuine offers."

There are several reasons why you can now get airborne for less. In the old days (pre-1994, when British Airways launched its highly successful World Offers scheme), airlines would try to predict how full each flight was likely to be - while the 8am to Paris was likely to be bursting at the seams, the Tuesday lunchtime flight would be comparatively empty. So they would sell blocks of seats at a hefty discount on the emptier flights to consolidators; these bulk-buyers would sell the seats at cheap prices, through "bucket shops". This still goes on, but British Airways has set up a sophisticated "capacity management" scheme that means it can predict the availability of empty seats very accurately, and offer them at highly advantageous prices - cut by an average of a third. British Airways sells these tickets direct, or via high street travel agents. Current destinations include Geneva and Munich from pounds 96, Sydney and Melbourne from pounds 699, Miami from pounds 269, Bermuda from pounds 381 and Belfast from pounds 55.

Another help is that since January 1993, the whole of Europe's air-route network has been deregulated. "Prior to then, it was a very lengthy process to get a licence to operate an airline, and as well as that it was necessary to get a separate licence for every route travelled," explains a spokesman for the Civil Aviation Authority. "Now an EU-owned airline can fly anywhere within the EU without asking for an individual route licence. If there are more than two operators on a route, the competition brings the prices down." This has been particularly apparent on routes between London and Scotland, where small operators such as Ryanair and EasyJet have helped bring prices tumbling - to as little as pounds 59 return, pounds 29 one way, on some routes. Prices to Dublin are also low: CityJet, a franchise partner of Virgin, offers return tickets from as little as pounds 59.

At the same time, bucket shops have been brought into the protective Air Travel Organisers' Licensing Scheme. "This has existed for many years, giving financial protection to passengers booking package holidays that include flights," says the CAA. "We have been extending what that covers for some time, and now it also includes bucket shops. The rule now is that unless the consolidator has a direct agreement with the airline they must hold an Atol licence." Hip, hip hooray. Time to book for the summer.

8 For further information, call: British Airways 0345 222111 (local call rates); CityJet 01293 747146; EasyJet 01582 445566; Ryanair 0171- 435 7101; STA Travel 0171-361 6100