Q. I have just been given a price of £516 for a Virgin Atlantic return flight to Las Vegas in February 2013. Should I book now or is this likely to go down? John Knight
A. It's the Hamlet dilemma, familiar to anyone booking a trip a fair way in advance – to buy, or not to buy, a flight at a particular moment? In a perfect world, from the airlines' point of view, fares would only ever increase: early bookers would be rewarded for committing cash upfront. Fares would increase steadily, on the principle that the closer to departure you book, the more you pay – with very late bookers handing over a fortune.
But given the fickle nature of the travelling public, and the behaviour of rival carriers, it is quite possible for fares to fall.
Airlines use "revenue management" systems that are intended to fill as many seats as possible on each flight while extracting the maximum cash that each passenger is prepared to pay. Fares fluctuate frequently: prices are nudged up or down to keep bookings on trend. In the case of a flight from Gatwick to Las Vegas, the airline will expect that by 1 October perhaps 30 per cent of seats on the departure on 1 February to have been filled. If bookings are heavier than predicted, fares will rise; if lower, then prices may be cut.
To add an extra layer of complexity, airlines often seek to boost the number of seats filled across the board by staging short-term "seat sales"; for example, British Airways has just finished a post-Olympics sales push that expired last night.
The competitive landscape to Las Vegas is also changing. At present, Virgin flies from Gatwick (and Manchester), while BA flies from Heathrow. However, next month, BA is launching flights from Gatwick to the Nevada city, in competition with Virgin.
Despite the new competition, you should seize the £516 deal on offer. Even under the latest BA sale, the lowest fare was £563 return. A future sale could conceivably see fares cut to, say, £499 return. If this happened, it would apply only to lightly booked flights, so you might not get the departures you want. So book now.