Windy city: Chicago / Getty


Q. I see Air Passenger Duty is being cut for under-12s. For the rest of us it's still way too high. Can I avoid it by booking a Dublin-London-Chicago ticket and just checking in at Heathrow? David Burke, Preston

A. No. Next April, the tax on anyone aged two or older flying from Britain to the US rises from £69 to £71. By May, children under 12 travelling in economy will be exempt, and from March 2016 everyone under 16 will escape Air Passenger Duty in every class. But most UK airline passengers will still pay one of the highest travel taxes in the world.

Some travellers boarding at British airports escape Air Passenger Duty by virtue of being in transit: arriving from a foreign country and connecting to another flight. That is one reason Ireland-UK-US fares are lower than for direct UK-US flights; another is that airlines can charge a premium for non-stop service, but conversely must offer cheap deals to tempt passengers to book indirect trips. Combining the two, a Dublin-Heathrow-Chicago flight is very likely to cost less than a Heathrow-Chicago trip on its own.

So what's wrong with your cunning plan? Well, the airlines regard the practice as "tariff abuse" and have a simple way to deal with it. They insist that every flight in your itinerary is taken in the right order. Fail to check in for the Dublin-Heathrow leg of your trip, and your entire itinerary will be cancelled.

Having said all that, if the savings are really substantial then it could be worth getting a cheap flight to the Irish capital in order to board a Dublin-Heathrow flight that connects to the US. But to save all that trouble, consider booking a Manchester-Dublin-Chicago trip on Aer Lingus. Build in a minimum 24-hour stopover and your APD liability falls from £71 to £13. The same applies for trips via Paris, Amsterdam or Reykjavik in Iceland.