Soaring fuel prices and the strength of the US dollar are threatening increases of up to 10% in the price of many of next summer's holidays.
Long-haul travellers will be worst affected. The longer the flight, the more important fuel becomes as a proportion of overall costs. Airlines pay for that fuel in dollars. And hoteliers and other suppliers in other countries besides the US - notably in the Caribbean and Latin America - set their rates in dollars. It all adds up to a very nasty combination of economic punches.
But its impact on tour operators is mixed. Those yet to publish long-haul programmes for next summer may have to up their prices by around 10%. The response of those with brochures already out will depend on whether they offer no surcharge guarantees - and on the extent to which they have bought dollars at a fixed rate in the forward market and their agreements with airlines.
Some firms whose booking conditions allow them the option of surcharging are struggling to avoid doing so by swallowing the extra costs. In any case, operators are forbidden by law from doing so less than 30 days before the customer departs. They must absorb extra costs up to 2% of the holiday price, and clients may cancel without penalty if the extra charge exceeds 10%.
Most big operators promise not to surcharge - but that may not stop them issuing updated editions of their programmes, with higher prices.
They could also follow the course adopted by long-haul specialist Kuoni, which, when customers telephone to book, is quoting higher prices on some packages than those shown in the brochure. For example, it is adding £68 per couple to the all-inclusive brochure price of £1,033 in late January at the Rex Turtle Beach on Tobago. The firm will not surcharge customers after a booking has been made, however, and a spokeswoman adds: "We are trying to offset these cost increases by re-negotiating our deals with suppliers."
Noel Josephides, managing director of Sunvil, says price rises in Europe will be offset by an 8-10% strengthening of sterling against key currencies such as the Greek drachma. But this will not be enough to balance rate increases imposed by hoteliers and higher flying costs. The net result could be an increase of 5-6 % in next summer's package prices, adding about £22 to a £450 holiday.
But it is the firm's long-haul customers who will bear the brunt. "Our Namibian programme won't be as badly hit because we pay hotels in rand. But in Central and South America and Zambia we are charged in dollars. I reckon we'll have to raise our prices to those countries by about 10%."
Journey Latin America warns that its prices in its latest escorted-tours brochure, which is about to be published, will have to rise "significantly".
Director Brian Williams says: "So far the problem is the strength of the dollar. Fuel price rises haven't fed through yet."
Some US airlines have already slapped a $20 per round trip fuel surcharge on domestic fares. But carriers flying to South America are in a bind. Their costs are rocketing but over-capacity, particularly in winter, continues to produce a flow of bargain fares.
