The proposal has a neat logic. Instead of contributing to even more atmospheric pollution by using mileage for additional trips, bmi’s Diamond Club frequent flyers would be helping to reduce CO₂ emissions. Typical emission-offsetting schemes include investment in renewable energy sources or, more controversially, tree planting.

The carrier already offers Diamond Club members the opportunity to convert their miles into cash donations to the charity Save the Children. It is not the first airline to get involved in offsetting. British Airways’ website gives passengers the option of calculating their CO₂ emissions on the flight they are booking and making a voluntary cash contribution to compensate. However, it does not offer offsetting through its BA Miles mileage programme.

bmi’s idea draws a mixed response from business travellers. Rob Angell, a director with mediation and facilitation services business RK Partnership, would prefer to see the airline prove its green credentials in other ways. “What would impress me would be if it broke ranks with other carriers by acknowledging the impact of its environmental footprint,” says Angell, who routinely pays to offset his business flights.

Andrew Harrison, marketing manager for a large telecommunications company and also a frequent business traveller, gives a qualified welcome. “I would go for it,” he says, “although in my opinion companies should be forced to offset the emissions caused by employees who travel on their behalf.”

Harrison’s remarks echo the opinion of other corporate travellers as well as environmental organisations and a growing number of businesses, all of which feel that it is the employer, not the employee, which should take responsibility. BA’s experience to date suggests individuals will not pay of their own volition. It says that contributions to its offset initiative have been “fairly slow”.

This confirms a recent survey by the travel management company Portman Travel. It found that although 62 per cent of employees believe their employers should pay to offset business travel’s contribution to climate change, 77 per cent are not prepared to sacrifice their own benefits to help.

Portman head of customer development Barry Fleming says employers are realising they need to take responsibility. “There is high public awareness of the relationship between travel and global warming but that is not translating into business travellers taking radical action,” he says. “On the other hand, companies are alive to it because corporate social responsibility (CSR) is a big issue for them. Larger organisations now have employees who deal directly with CSR.”

As a result, Portman has launched a programme in conjunction with the CarbonNeutral Company which helps corporate clients calculate their travel-related CO₂ emissions and make the relevant offset contributions.

Like Harrison, Friends of the Earth (FoE) believes a green levy on air travel should be compulsory rather than voluntary, but says it should be in the form of taxing aviation fuel. “The bmi idea sounds like a way of people clicking a button to offset their guilt,” says its aviation campaigner, Richard Dyer. “BA’s experience shows hardly anyone takes up these ideas anyway. We need action from governments, not voluntary schemes. We don’t ask people to pay voluntary taxes for their cars.”

According to FoE, air travel accounts for six per cent of the UK’s CO₂ emissions. Dyer says businesses need not only to offset flights but to cut down on their flying. His view is gaining support within corporate circles. HSBC has committed itself to becoming a carbon-neutral organisation but earlier this month the bank’s head of global business travel management, Tony Pilcher, said businesses must go further. “Offsets are not getting to the heart of what our responsibility is… we have a responsibility to reduce business travel,” he told the Institute of Travel Management’s annual conference in Manchester.

Several corporate travel managers at the conference described pursuing a twin strategy of making offset contributions and finding alternatives to flying. One major professional services firm is preparing to announce to travellers that they must use rail instead of air for domestic UK journeys and trips to Paris and Brussels.

Another business pursuing both ideas is Credit Suisse. In 2004, it reckons travel by Swiss-based employees was responsible for 140,000 tonnes of CO₂ emissions, accounting for one-third of all emissions by the group’s Swiss operation. Credit Suisse has committed to paying SFr3 (£1.30) for every hour of flying by employees, which landed it with a bill for SFr146,000 (£64,000) in 2005.

At the same time, Credit Suisse is exploring alternatives to travel. “We are internally promoting video- and web-conferencing,” says Patrik Burri, a vice-president in charge of the group’s environmental management. “Our use of virtual conferencing worldwide rose 14 per cent in 2005, while our growth in air mileage was zero.”

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