Just a day after Virgin Atlantic revealed it is to undertake the first test flight of a biofuel powered airliner, BA yesterday made a play for environmentally-conscious passengers with the news it is to revamp its carbon offset scheme and support research into aviation's contribution to global warming.

The airline said that the scheme had been upgraded to ensure that it only includes carbon credits certified through the UN's clean development mechanism (CDM), which experts claim uses more demanding criteria many offset firms.

Under the new scheme the company said it would invest in a new wind farm in China, as well as run-of-the-river hydroelectric plants in China and Brazil.

"We were the first airline to offer carbon offsets, and we intend to remain at the forefront in this area," said Silla Maizey, head of corporate responsibility. "The UN framework guarantees that offset payments will lead to genuine reductions in emissions through the projects we have chosen with our new provider, Morgan Stanley."

Some offset operators have claimed that CDM criteria - which are expected to be used as the basis for the government's upcoming best practice guidelines for the offsetting sector - are too demanding and result in high administration costs that exclude many smaller but still environmentally beneficial projects from entering the scheme.

BA also announced that it is to invest in a number of projects to protect the Brazilian rainforest and contribute to new research from Cambridge University into the impact of non-CO2 gases from aviation on climate change.