Co-op travel firm Travelcare is the first high street firm offering customers the chance to counter the environmental impact of their flights.
Aviation is the fast growing source of carbon dioxide
Customers will be able to invest in overseas schemes, run by Climate Care, aimed at reducing carbon emissions.
Such "offset" schemes, whereby the amount invested can vary to reflect the the flight's emission levels, have only been available on the internet.
Aviation is the fastest growing source of carbon dioxide.
The overseas projects include schemes in India and Uganda ranging from wind farms to more efficient cooking fuel.
Dave Smith, a spokesperson for the Co-op group, said the scheme allows individuals to make "some contribution" towards countering climate change.
But Mr Smith added: "We are not for one minute suggesting this is the answer to [resolving] climate change."
Travelcare will start by offering a pilot scheme, before rolling it out to all 340 outlets, "making it as simple as other travel purchases".
Customers could chose how much they wanted to pay and whether they wanted to "offset" the entire flight or part of it.
Offsetting a flight to Australia would cost £50, while a flight to France would cost £3.
Such offsetting schemes have been criticised by environmentalists for enabling people to continue flying, without making the deeper changes necessary.