Britain is spending half a billion dollars to upgrade 28 of its seven ton Puma helicopters. These aircraft first entered service in the early 1970s. In addition to replacing any worn structural components, the upgrade includes new engines, electronics and controls. A missile warning and defense system will also be installed. The Puma has a cruising speed of 250 kilometers an hour, endurance of about two hours and can carry up to 16 passengers or two tons of cargo. The refurbishment will keep the Pumas going for another 13 years.