The world's most expensive military aircraft is the US-made B-2 Spirit, which cost in excess of $1.3 billion (£780 million) per unit.A long-range multi-role bomber, it is capable of delivering both conventional and nuclear munitions, and has a number of stealth characteristics that enable it to penetrate an enemys defences without being observed: these include its special coatings and flying-wing design. The B-2 has an unfuelled range of 9,600 km (5,965 miles), and can carry a payload of 18.144 tonnes. It made its first flight on 17 July 1989.During 30-hour bombing missions to Kosovo in 1999, B2 pilots used decidedly low-tech equipment on which to steal naps: plastic US$8.88 lawn lounger chairs from Wal-Mart slotted in behind the seats in the cockpit.