Q. My wife, our daughter and I are going to Gran Canaria over new year. Our daughter has, thankfully, landed a job, and needs to fly back before us. We're flying from Gatwick with easyJet, and are all on the same booking. Should we just throw away her ticket and buy a new one, or can we change the date of just one flight?
A. Thankfully, easyJet makes it straightforward to change one flight on a multiple booking without affecting the others. At easyJet.com use the "manage booking" option. You should be presented with a full set of the family's flights. You can then select only your daughter's inbound trip, using the tick-box. You will be presented with the familiar booking display, and can choose an earlier flight on the same route (or, for that matter, any other flight on the easyJet network).
You will pay a fee of €42 (about £35) for the change, plus any increase in fare between the existing flight and the new one. Suppose you booked the old flight good and early, paying say €100, and the new one is now €200: you will pay a total of €142 (about £115). But at least you are getting some credit for the original flight.
Three more quick points: if by any chance the new flight is cheaper than the old one, you don't get a refund of the difference. In rare circumstances (and not from the Canaries at Christmas) the new flight will cost less than €42, and therefore it is not worth switching. And you could always check the excellent search engine, skyscanner.net, to see if another airline is by any chance offering a suitable flight to Gatwick cheaper than €142. If so, buy it - and either throw away the existing flight, or choose another trip entirely, later in the year, on which to "spend" the credit you have.