The first of 48 of the latest version of C-17 (Block 13) has been delivered. One or two a month are being built. Costing about $200 million each, the latest version can carry more fuel (enough to stay in the air another 4-5 hours.) New radar equipment allows for flying lower in bad weather and in formation (for dropping troops or supplies by parachute). The Block 13 improvements will be added to older C-17s when they are due for major maintenance. Because of the war in Afghanistan, and the need for air transport, it's now expected that at least 180 C-17s will be built, although the U.S. Air Force would like 222 (or more.)