3 weeks ago, on a United Express flight from YWG to ORD, I made an in-flight purchase. This was obviously in US Dollars, and I paid with a travel money (prepaid) Mastercard issued in the UK, and denominated in US Dollars.

On my statement, it shows that the transaction was processed in Hounslow (Heathrow), and as it was a "domestic" transaction, I was charged an additional fee by my card issuer.

Are US cardholders being billed for in-flight purchases from the UK, or is United trying to do something clever by working out the issuing country of my card.

My card issuer is pretty insistent that although as a customer, I would have no way of knowing that the transaction would be processed in the UK, that they're not responsible for where a merchant processes the payment, so I'm curious to investigate further.

Think it's a bit unfair if customers are being assessed fees for a transaction because of where UA is processing the payment.