The U.S. Navy is looking for a new COD (Carrier Onboard Delivery) aircraft. It is now using 35 aging C-2s (cargo versions of the E-2 radar aircraft, in effect, C-2 is an E-2 without the saucer like radar container above the fuselage, and all the electronics inside the fuselage). The C-2 can carry 4.5 tons of cargo (or 26 passengers), per sortie, to or from a carrier. Cruise speed is 460 kilometers an hour, and range is over 800 kilometers. The current C-2s are over two decades sold, and are being refurbished so they can go for another decade.
Since the navy has agreed to buy 48 V-22 tilt rotor aircraft, but has yet to decide what it would do with them, the COD mission seems like a suitable job. Both aircraft weigh the same (about 25 tons). The U.S. Marine Corps MV-22s can carry 24 troops 700 kilometers (vertical take-off on a ship, level flight, landing, and return) at 400 kilometers an hour. As a COD aircraft, the V-22 is similar as the C-2. That means a slightly slower (445 kilometers an hour) cruise speed, and the V-22 is more expensive to maintain, but can land on carrier more easily (as a helicopter) and can carry loads of up to 4.5 tons slung underneath. This enables the COD to deliver outsize objects (replacement components or structures for the ship, or aircraft parts that would not fit inside a C-2 (or V-22.)
The V-22 is the first application of the tilt-rotor technology in active service. The air force is already working on improvements (to make the V-22 more reliable and easier to maintain), but these won't be installed for another few years. The V-22 gives the marines and SOCOM a lot more capability, but, as it often the case, this is a lot more expensive. The initial production models of the CV-22 cost over $60 million each. SOCOM insists on a high degree of reliability for its aircraft. Thus the navy could get a cheaper replacement for the C-2 if it bought a similar aircraft. Not a big savings, because taking a commercial aircraft and "navelizing" it for carrier operations is expensive.