Chancellor George Osborne announced the changes in his Autumn Statement of 2014.

Those who had already booked flights will have the tax refunded - but there are differences in the way airlines are dealing with those payments.

APD was abolished for the under 12s from 1 May last year, bringing a programme of refunds from airlines.

Hannah Maundrell, editor of comparison website Money.co.uk, said: "As airlines breathe a sigh of relief having just completed the first batch of refunds, they now have to start the whole process all over again.

"This would be a straightforward process if all refunds were automatic. Sadly, some travel companies are asking people to 'apply' for a refund. This could lead to people being left in APD limbo as one in three parents claimed they would not apply for a refund.

"Just to add further complexity, parents that booked package deals will have to go back to the tour operator to make a claim, not the airline."

Air passenger duty is charged on all passenger flights from UK airports. The rate of tax varies according to where the passenger is going, and the class of travel, starting at about £13 for short-haul flights to Europe.