20 Percent of all US Marines Aircraft Are Grounded, F/A-18 Hornets The Most Affected

Nearly one of every five of the Corps' aircraft are unable to fly, making it difficult for Marines to train for deployments.
The shortfall spans across aircraft in the fleet, and it is largely caused by a backlog of aircraft stuck in depots for extensive work and overhauls. The problems date back to the 2013 defense budget cuts.
The problem is most prevalent with F/A-18 Hornets, but also impacts CH-53E, AV-8B Harriers, MV-22B Ospreys, and H-1 Hueys.
The strike-fighter shortfall could reach as high as 134 aircraft. The gap is caused by a service life extension program that has caused a backlog of Hornets in short-staffed maintenance depots.
Legacy Hornets were brought into depots to extend their service life from 6,000 flight hours to as long as 10,000 in order to keep them operational until the F-35B entered the fleet. The Hornets were only designed to last to 6,000 hours, and when engineers opened up the airframe to extend their service life, they found unexpected levels of corrosion that required extensive work.
Sequestration also made it tough to buy spare parts for aircraft, so even aircraft that are in the fleet sometimes can't fly.
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