Simon Calder explains what you need to know about changes to the Air Miles system

With British Airways overhauling its frequent-flier points system, many have reacted angrily, believing that the airline has "devalued" their Air Miles.

It's not quite like that and Senior Travel Editor Simon Calder provides a quick, three-minute guide to what you need to know about the radical changes announced to the Air Miles system by BA.

Millions of economy-class passengers earn fewer points and face paying more to redeem them while business travellers will accrue frequent-flyer points even faster.

British Airways, which invented Air Miles – now known as Avios – said the changes will come into effect on 28 April.

Under the current scheme, an economy return flight from Heathrow to Vancouver earns 9,400 points – enough for a round-trip from London to Milan, subject to a £35 payment. But some economy passengers face a 75 per cent drop in the number of Avios earned, which will see them accrue a meagre 2,350 points.

Conversely, business-class and first-class passengers on the same plane will see a 9,400-point rise, with the increase alone providing enough Avios for a free flight to Italy.