To recap: the surcharges were introduced as a way for the airlines to distance themselves from the rising cost of oil, in the same way that they itemised government taxes on their bills.

Travel writer Simon Calder explains: "It was a way for the airline to say "this is nothing to do with us - don't blame us for the price rises".

Lufthansa is slightly more illuminating. It introduced an "international surcharge" in 2014. Spokesman Boris Ogursky says: "The surcharge covers costs beyond our control such as air traffic control fees, emissions trading scheme payments and so on.

"It is important for the customer to compare the overall cost of the flight with other airlines. The total fare is steered by market competition - it's not just us making up surcharges and putting them up and down as we like.

"It is a highly competitive marketplace."

Japan’s airlines are set to remove fuel surcharges with oil trading around a 12-year low, ending a decade of high jet kerosene costs that had added as much as 66,000 yen ($563) to the price of a round-trip ticket to the U.S. or Europe.

If Japanese airlines do remove surcharges, they would merely be catching up with some of their counterparts elsewhere. South Korean airlines haven’t levied fuel surcharges on overseas flights since last September, under a government-set formula that’s adjusted every month to reflect international crude prices.

Budget carrier AirAsia Bhd., AirAsia X Bhd. and all their affiliates removed fuel surcharges last January. Qantas Airways Ltd. began folding the surcharge into its base ticket price a year ago, adding that its international fares wouldn’t change as a result.

In an e-mailed statement Monday, Singapore Airlines Ltd. said it regularly reviews its fuel surcharge levels, “and whenever changes are decided upon we announce them to the market.” Singapore Air and its regional unit SilkAir lowered surcharges in February 2015.

Cathay Pacific still imposes a fuel surcharge, according to a travel advisory issued Dec. 29. In an e-mailed response, Cathay said airlines submit applications to Hong Kong’s Civil Aviation Department for fuel surcharge approval each month.

Airlines don’t publish similar surcharge schedules, and the vagueness serves an important purpose: Many big-volume corporate travel buyers get their airline discount applied to base fares, while surcharges are paid in full.