I live in Dubai and have tried to book flights from Dubai to London in August with BA, Virgin and Emirates. The price seemed high, and out of devilment I tried to see what the prices would be if I were to be travelling in the opposite direction on the same days. I was astonished to see that there was a difference of between £437 and £784 for a family of four. Can you explain why this is so? Andy Bonito, Dubai

Doc Holiday responds: Finding such a disparity can be utterly frustrating, but while there are rules governing airline pricing within particular countries (prohibiting unfair competition, price fixing and the like), there are no rules to say that a flight from A to B should cost the same as a flight from B to A.

Like other companies operating in a global free market, airlines will try to maximise their revenues and profits by selling their goods at different prices in different places. For the same reason, designer jeans and cars also sell for different prices across the world.

As long as an airline complies with local regulations on taxes and anti-competitive behaviour etc, they are free to determine fares as they like.

A BA spokesperson said that the airline sets prices in accordance with "local market conditions, and the supply and demand for seats". He wouldn’t be drawn on what specifically they might be.

No two flights book up in exactly the same way, and looking at fares for the same city pair on the same day, but in a different direction, you’ll be unlikely to find the same fares. For example, weekends fall in a different part of the week in the Gulf, peak holiday time comes in a different month to the UK, and there are also local festivals, events, and trends, which will also effect demand. And as a flight becomes more full, the remaining seats tend to become more expensive.

That said; the majority of the price difference that you have discovered is probably due to more general market conditions. If in general, passengers originating in Dubai are prepared to pay more than passengers originating in London, then overall the airlines will charge more. In the case of Dubai, there is a high per capita wealth, a great propensity to make last minute bookings, and to travel in large family groups.

It really is a question of supply and demand.

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