Boeing and Virgin Atlantic announced Tuesday an environmental partnership that includes a joint biofuel demonstration aimed at developing sustainable fuel sources suitable for commercial jet engines and the aviation industry.

Boeing also announced that Virgin Atlantic has ordered 15 787-9 Dreamliners, worth about $2.8 billion, with options for an additional eight 787-9s and purchase rights for an another 20 787s.

The order was previously listed on Boeing's Orders and Deliveries Web site and attributed to an unidentified customer.

The biofuel demonstration is scheduled for 2008 using a Virgin Atlantic Boeing 747-400, and is  being developed jointly with GE Aviation and Virgin Fuels.

Boeing and Virgin Atlantic are also collaborating on reducing fuel burn and cutting aircraft emissions on the ground by exploring alternatives to traditional aircraft operations at airports.

The two companies are partnering on trials of towing airplanes to "starting grids," areas close to the active runway to start engines preflight, with a goal of reducing fuel consumption and carbon emissions by up to 50 percent, as well as limiting community noise.

So far, trials conducted at London's Heathrow and Gatwick Airports and San Francisco International Airport have produced positive results, and work continues to develop alternative operational procedures at the world's busiest airports.

"Working together in partnership, Boeing and Virgin Atlantic will develop innovative, environmentally progressive solutions to provide greater fuel efficiency and lower aircraft emissions," said Scott Carson, president and CEO, Boeing Commercial Airplanes.