It may be the ultimate form of aero-recycling... recrafting solid older airframes with the latest technology and aerodynamic improvements, with the result being very economical high-performance aircraft available for a fraction of the cost of their "newer" counterparts.
In the case of Nextant Aerospace, they saw incredible potential in the ruggedly capable Beechjet 400A/XP. The bird built a reasonable amount of market share due to its cabin size, speed and reliability -- and its a favorite for a number of operators. But... Nextant thought the bird could use some updating, especially in terms of range. The standard 400A/XP has a range of 1333 nm with 4 passengers and IFR reserves and uses an elder Pratt and Whitney JT15D-5 engine and nacelle configuration. While the JT15D was a great engine, it was an early entrant in the high bypass turbofan game and does not remotely boast the efficiencies of more recent designs.
It didn't take much to see that the installation of Williams FJ44-3AP’s along with new aerodynamically improved engine nacelles could turn the bird into a whole new beast... and it did. Range increased by 50%, long-range cruise speed by 6%, S/E Climb rate by 144%, Time-To-Climb to FL430 decreased by 33%, and operating costs were boasted to be as much as 30% lower.