Boeing started assembling its Joint Unmanned Combat Air Systems (J-UCAS) X-45C aircraft on June 8, 2004, loading the aft "carry-through" frame into a holding fixture inside the company's St. Louis manufacturing facility. The 86-pound aluminum part, which spans the back end of the vehicle, will soon be mated with the two X-45 engine keels. The X-45C vehicle will be able to cruise at 0.85 Mach, with a 4,500-pound payload, and fly at 40,000 feet with a mission radius of 1,300 nautical miles.