The Hawker 400XP incorporated aerodynamic, mechanical and interior improvements from the Hawker 800XP. In October 2008, Hawker Beechcraft upgraded it as the Hawker 450XP including new, more fuel efficient Pratt & Whitney PW535Ds with 2,965 pounds of thrust each, but it was canceled in June 2009 due to poor economic conditions. Nextant Aerospace re-manufactured it as the 400XT, replacing the JT15Ds with Williams FJ44s and adding new avionics and interior. It was FAA-certified in October 2011. Up to one-third of the 400A/400XP fleet could be retrofitted, enabling improved range, speed and fuel efficiency. It should keep their resale value to remain in economic service for another twenty to thirty years, like Falcon 20s reengined with TFE731s. The type is used by many corporate and private users, it is also used by air-taxi and air charter companies. In 2014, most were U.S. registered, a majority with single aircraft operators. Flight Options and Travel management co. were its largest operators as NetJets Europe has disposed of its fleet. The second highest concentration was in Mexico, then Brazil, the rest were scattered throughout the world. The USAF operated 178 T-1A Jayhawks. Charter and fractional operators fly at least 800 to 900 hours per year while most corporate operators fly 300 to 400 hours. In 2014, 400A values range from $500,000 for mid-time 1990 models to $1.3 million for 2003 models, a 2004 Hawker 400XP commands about $1.5 million and last 2010 models were listed at least for $2.5 million.