The Navy's has replaced or is about to replace many of its older aircraft.
The Navy most recently retired the F-14 Tomcat, a 1974 vintage plane in its original version, which was one of two kinds of fighter aircraft used from its aircraft carriers. The other is the F-18 Hornet, which was introduced in its original version in 1983. The AV-8B Harrier, a Marine vertical landing fighter aircraft can land on a carrier, but is rarely used with one (more often, they are deployed from Wasp and Tarawa class amphibious assault ships, which are about the size of most foreign aircraft carriers). The F-18 and AV-8B, will eventually be replaced by the F-35C and F-35B respectively, but those planes are not yet ready for action. (The current problem with the F-35B is that its exhaust is so hot that it melts the material currently used for ground based temporary runways.)
The Navy used to use the A-6 fighter, a carrier based attack aircraft, but now, the only remaining planes in that class have been converted to an EA-6B Prowler electronic warfare version starting in 1971. About 68 of them remain in service, and they will be replaced starting in 2008 (July 22 entry) with an F-18 based replacement, the EF-18G (the Growler).
The Navy has also retired the H-3 Sea King helicopter, a 1961 vintage in the original version, which has over time been replaced by the H-60 Sea Hawk helicopter (a naval version of the Army Black Hawk), a model which entered service in 1983.
One of the main uses for the H-3 had been in anti-submarine warfare, and two other aircraft used for that purpose, the carrier S-3B Viking, also a 1974 vintage, is now designed a "sea control" aircraft and scheduled for removal from service without replacement by a new version around 2009, while the P-3 Orion, which entered service in 1962, is currently being replaced over the next few years by the P-8 MMA (multi-mission aircraft), a Boeing 737 based design.
Meanwhile, the V-22 Osprey is about to enter service with the Marines and will serve primarily as a replacement for CH-46 Sea Knight, a helicopter model introduced in 1964 for medium lift duties (25 troops).
The CH-53 Sea Stallion, the 1962 vintage heavy lift helicopter (the heaviest in the U.S. military, primary used by the U.S. Marines) has no planned replacement. The other two main naval aircraft, the E-2C Hawkeye (a carrier based airborne radar plane), a 1964 vintage with about five dozen in service, and the C-2A Greyhound (a carrier based small fixed wing transport), also an older plane with about 19 of them in service right now, are not scheduled to be replaced in the near future.
The bottom line is that the Navy's aviation resources are reasonably modern, if not necessarily right at the cutting edge.