The U.S. Navy retired its F-18C “Hornet” fighters in 2019. Some will still be flown by reserve units to represent enemy aircraft during “adversary training.” The U.S. Marines will continue to use their F-18Cs until at least 2030 and so will most foreign users. The F-18 A/B/C/D was in production from 1974 to 2000 with 1,480 built. The most widely used (75 percent) model was the single-seat F-18C. Some F-18Cs were built with two seats for training or complex missions. Some of those were later modified with the back seat replaced by special electronics gear.
The U.S. Navy was the first and largest (about half) user. Add those used by the marines and that accounts for about 60 percent used by Americans. The rest were purchased by export customers Australia, Canada, Finland, Kuwait, Malaysia, Spain and Switzerland. These nations are phasing out the F-18C or seeking a replacement. Australia sold 25 of its retired F-18Cs to Canada, which is still seeking a suitable replacement. Australia, like many other F-18C users, is adopting the F-35.
It will take a decade to replace all F-18Cs with F-35s. The U.S. Navy could afford to get rid of all its F-18Cs by depending on the larger and younger F-18E. Despite the similar name, the F-18E is actually a different aircraft that entered service in 2001. About 600 of these have been built and some of them will still be in use by 2040. The U.S. navy and marines are eventually replacing all their F-18s and Harriers with F-35s. The F-18 that will probably serve the longest is the F-18G electronic warfare aircraft, which is based on the two-seat F-18F. The F-18E and G are still in production, which is not expected to end until the late 2020s.
The navy began to realize, about a decade ago, that their F-18Cs would have to be retired earlier than expected. This was confirmed in 2010 when the navy grounded 16 percent (104 of 635) of its older (A/B/C/D models) F-18 fighters. The reason was the discovery of cracks in the airframe. Small cracks were expected to show up eventually, the result of all the stress put on the metal from violent aerial maneuvers and carrier landings. But in this case, the cracks were showing up sooner than expected. Most of the grounded aircraft could still be flown in an emergency. All these older F-18s had to be examined, and, for those found with cracks (usually where the wing meets the fuselage), temporary repairs could be made.
Since about 2006 the navy found that both their older F-18C Hornet fighters and their newer F-18E "Super Hornet" were wearing out faster than expected. This was sort of expected with the F-18Cs, which entered service in the 1980s. These aircraft were expected to last about twenty years. But that was based on a peacetime tempo of operations, with about a hundred carrier landings (which is hard on the airframe) per year. There have been more than that because of the 1991 Gulf War (and the subsequent decade of patrolling the no-fly zone) and the war on terror. So to keep enough of these aircraft operational until the F-35 arrives to replace them, new structural components (mainly the center barrel sections) were manufactured. This is good news for foreign users of the F-18C, who want to keep their aircraft in service longer.
The F-18E entered service in 2001 and was supposed to last 6,000 flight hours. But the portion of the wing that supports the pylons holding stuff (bombs, missiles, equipment pods or extra fuel tanks) is now expected to be good for no more than 3,000 flight hours. The metal, in effect, is weakening faster than expected. Such "metal fatigue", which ultimately results in the metal breaking, is normal for all aircraft. Calculating the life of such parts is still part art, as well as a lot of science. Again, unexpectedly high combat operations are the culprit. One specific reason for the problem was the larger than expected number of carrier landings carrying bombs. That's because so many missions flown over Iraq and Afghanistan did not require F-18Es to use their bombs or missiles.
The navy modified existing F-18Es to fix the problem, which is a normal response to such situations. Sometimes these fixes cost millions of dollars per aircraft, but this particular fatigue problem is costing more to fix than expected. Many aircraft appear beyond repair and will have to be retired after 8,000 hours in the air.
There are actually two quite different aircraft that are called the F-18 (the A/B/C/D version, and the E/F/Gs). While the F-18E looks like the original F-18A, it is actually very different. The F-18E is about 25 percent larger (and heavier) than the earlier F-18s and has a new type of engine. By calling it an upgrade, it was easier for the navy to get the money from Congress. That's because, in the early 1990s, Congress was expecting a "peace dividend" from the end of the Cold War, and was slashing the defense budget. There was a lot of commonality between the two F-18s, but they are basically two different aircraft. Thus when used more heavily than expected, they developed metal fatigue in different parts of the airframe.