TVL4Free.

The US Banking system Debit Card system is completely different to the UK Debit Card System.

If you use a US VISA debit Card at any point other than a Swipe Machine, it ceases to be a Debit Card and Becomes a Credit Card with VISA applying Credit Card charges to The Retailer.

Their is no Interbank Debit system between any banks outside the USA, therefore all charges have to go via The Visa centre hence the higher charges.

Incidently I do not know of one US Airline Site that accepts foreign issued Debit Card, the only exception being American when you book through their UK site www.americanairlines.co.uk and this links to the UK Banking system.