(I think this belongs on Space/Science.  If it doesn’t let me know.  As for references, go to Wikipedia P-3 and Wikipedia P-8.)

The admittedly old Orion P-3 is being retired for a number of good reasons.  However, it or something similar could be built new again, with newer engines, newer materials, newer technology.  It was prop-driven and compared with many airplanes, slow.  However, it was faster-’n-hell compared to submarines.

The new anti-sub airplane is a modified Boeing 737, a proven airframe,  jet powered and faster than the P-3.  And examining the specs for each plane show it to be so inferior in performance as an anti-sub weapon to the P-3 as to defy credulity.

For one thing, anti-sub airplanes often operate at low altitudes.  Jet engines are notoriously inefficient at low altitudes.  This is reflected in the range.  Some of these specs are confusing.  For instance, the listed time on station for the P-3 is 3 hours, though the endurance is 16 hours.  But the total range for the P-3 is 4760 nmi and the total range for the P-8 is 1200 nmi, almost precisely 25% of the P-3.  And it’s important that an ASW plane be able to loiter for a long, long time.

I can understand replacing the present fleet.  I can’t understand replacing it with the P-8.

Performance P-3

• Maximum speed: 411 kn^[1] (750 km/h)
• Cruise speed: 328 kn^[1] (610 km/h)
• Range: 2,380 nmi radius^[1] (4,400 km)
• Combat radius: 1,346 nmi^[1] (2,490 km)three hours on-station at 1,500 feet
• Ferry range: 4,830 nmi^[72](8,944 km)
• Endurance: 16 hours^[72]
• Service ceiling: 28,300 ft^[1] (8,625 m)
• Rate of climb: 3,140 ft/min (16 m/s)
• Wing loading: 107 lb/ft² (530 kg/m²)

Performance P-8

• Maximum speed: 490 knots (907 km/h)
• Cruise speed: 440 kn (815 km/h)
• Range: 1,200 nmi (2,222 km)4 hours on station (Anti-submarine warfare mission)
• Service ceiling: 41,000 ft (12,496 m)