After a quarter century of using the Dassault HU-25 Guardian on sea patrols, the US Coast Guard is transitioning to the EADS CASA HC-144A Ocean Sentry which is based on the CN-235 transport. Though it may seem backwards to go from a pure jet to turboprop aircraft, the HC-144A carries the same fuel load as the HU-25 but burns it at half the rate which translates longer time-on-station, eight to nine hours versus the Guardian's four hours on-station. The per-hour operating cost has improved as well with the HC-144A costing less than $1000/hour compared to the Guardian's $1500-$1800/hour.
In addition, the HC-144A has a rear cargo door/ramp as well as a belly-mounted observation bubble allowing SAR crews to do something not previously possibly on other USCG aircraft- look below the aircraft. The last of the Guardians should be retired in 2020 (of the 21 in service now) and replaced with 36 HC-144A Ocean Sentries. Five are now in service with pilot training taking place at CGAS Mobile, Alabama.
Source: Air & Space Smithsonian, January 2009. "Then & Now: Frozen Moments as Time Marches On" by Paul Hoversten, p68.