AN empty passenger jet has been flown from Cardiff to Heathrow and back six times a week for the past five months simply to retain a runway slot at the London airport.
British Mediterranean Airways, which operates the 12 flights a week, was last night described as "extravagant and irresponsible" by environmental groups.
The airline claims it has operated the daily flights, which have left a massive carbon footprint, to ensure it continues to be allocated a runway slot at Heathrow - the busiest airport in the world for international flights.
The 124-seat British Airways Airbuses, under contract to BMed, have flown the 240-mile round trip six times a week since last October, (daily flight times vary) with each flight producing more than five tonnes of carbon dioxide.
They are estimated to have produced the same level of emissions as 36,000 cars undertaking the journey on the M4, despite not transporting any passengers.
The news emerged on the day the Conservative Party unveiled plans to give every person in the country an annual carbon allowance, designed to encourage greater personal environmental responsibility among frequent flyers.
The radical measure is one of a number being considered as the party pursues the green vote. Other options include the immediate imposition of fuel duty and/or VAT on domestic flights and then replacement of air passenger duty with a per-flight tax based more closely on actual carbon emissions.
The introduction of fuel duty has been fiercely opposed by airline companies, which claim it would be financially damaging.
But with the cost of BMed's "ghost flights", as they have been described, estimated to be up to £2m, environmental campaigners have seized on them as proof that fuel tax should be implemented immediately.
Gordon James, of Friends of the Earth Cymru, said, "It's totally unacceptable - it's almost criminal.
"Climate change is such a big issue - it's already impacting on people in poorer countries. People are dying because of it and this sort of extravagant and irresponsible behaviour has got to stop.
"Aircraft companies are complaining if anyone suggests that fuel should be taxed, and yet here they are, taking part in this nonsense of flying empty planes at a huge financial cost to themselves.
"If they can afford to do this, then they can afford to pay tax on fuel."
Every single one of the 1,250 daily landing slots at Heathrow are allocated to airlines, and is jealously guarded by their holders, but can be awarded to a rival if they are not used regularly.
A slot can be withdrawn from an airline if it is not used at least 80% of the time over a six-month period, and will then be reassigned by an independent body that coordinates take-off times.
Alternatively they can change hands for upwards of £10m.
David Richardson, chief executive of BMed, said the company had explored other options for retaining the slots, including leasing them to another airline or using smaller aircraft, but had concluded that flying an Airbus to Cardiff and back every day was the best option.
The flights are not advertised and do not appear on arrivals or departures boards.
Mr Richardson said the decision to fly the ghost flights to Cardiff was made after BMed, which operates routes to destinations such as Tehran, Beirut and Tbilisi, was forced to scrap flights to Tashkent, in Uzbekistan due to civil unrest there.
He said, "The Uzbek market had really collapsed, but we knew we would want to use those timings again this summer.
"It wasn't the ideal thing to do, but we wanted to keep hold of it.
"It is possible to do it more cheaply than we have done - in theory.
"Our difficulty was that with the timings we had, we needed an airport that was open all night.
"We looked at the alternatives, and Cardiff was the best option."
Graham Thompson, of the campaign group Plane Stupid, said, "These ghost flights very much undermine the greenwash we get from the airlines on how they are going to protect the environment.
"This shows they are willing to sacrifice the climate for a profit."
News of the flights will weaken the position of those airlines which yesterday offered strong opposition to the Tory proposals for the introduction of fuel duties.
In the foreword to a consultation paper, entitled Greener Skies, Shadow Chancellor George Osborne argued the existing system of aviation taxation was "fundamentally flawed" but that the answer was not to simply stop flying altogether.
He wrote, "However, I believe the case for acting now to reduce the future growth in greenhouse gas emissions from aviation is compelling. In particular, air passenger duty is not directly linked to carbon emissions and provides no incentives for airlines to use more fuel-efficient aircraft.
"I want to consult with the industry, with environmental groups, and with the public in order to create a sustainable regime of aviation taxation that has broad support."
But several airlines condemned the plan. Virgin Atlantic claimed that taxing passengers would damage the British economy. British Airways describing taxation as "an extremely blunt instrument" for cutting emissions.
Carbon emissions between Cardiff and London
Flying alone from Cardiff to London produces 5.21 tons of carbon dioxide
Flying on a plane full of passengers would produce on average 63.16kg per person
Undertaking the same journey alone in a medium-sized car would result in emissions of 37.9kg of carbon dioxide
By bus, that figure would be cut to 16kg per person
Travelling on a train would virtually halve that figure again to just under 8.5kg for each person aboard
For those energetic enough to cycle, or with enough time to walk, carbon emissions would be negligible