Silverjet, the first airline to vow carbon-neutral travel on all its flights, made its debut voyage Thursday, crossing the Atlantic from London to New York.

The business-class airline is offering its green-minded customers carbon credits, a type of voucher that is used to sponsor clean-energy research and projects. Silverjet touts the credits as a means to counterbalance carbon emissions produced through travel.

Mandatory carbon offset contributions are included in the price of Silverjet's tickets, which begin at £999, or about $2,300 Cdn.

Silverjet is the third business-class airline to offer service between London and New York, joining rivals Maxjet and Eos. Analysts say Silverjet may have a difficult time luring travellers away from some of the larger airlines, which offer flexible schedules and generous rewards programs. Still, Silverjet CEO Lawrence Hunt said ticket sales have surpassed the company's original forecast.

Carbon offset programs have grown in popularity in recent years to such an extent that the New Oxford American Dictionary chose the phrase "carbon neutral" as its word of the year in 2006.

"Being carbon neutral involves calculating your total climate-damaging carbon emissions (your 'carbon footprint'), reducing them where possible, and then balancing your remaining emissions, often by purchasing a carbon offset: paying to plant new trees or investing in 'green' technologies such as solar and wind power," Oxford University Press said in a release.

"It's more than a trend, it's a movement, which is why the editors of the New Oxford American Dictionary have declared carbon neutral the word of the year for 2006."

Critics say carbon offsets are a method of easing company and consumer guilty consciences with financial contributions while continuing to pollute the environment.

But advocates of carbon offset programs say they push environmental concerns to the forefront, encouraging consumers to be proactive. They say the offsets actively neutralize damage by supporting energy projects such as wind farms, tree planting and methane capture plants.