The Harrier is still flying. The F-35B is set to replace them but since that aircraft hasn't been manufactured in large numbers yet, the Harrier remains in front line service and likely will for many years to come.

> The U.S. Marine Corps has extended the retirement date of its AV-8B Harrier IIs in increments until 2030, and most of the fleet will remain active through 2027, according to Boeing, which supports the 1980s-generation strike aircraft. Harriers were originally scheduled for retirement in 2015.

You know, you're totally right. I was thinking of the British Harriers for some reason.

It's also worth mentioning that the Harrier is an older plane than the A10; by around ~8 years actually.

The Harrier is, but the thing actually in service (the Harrier II) is newer than the A-10.

Harrier introduced 1969

A-10 introduced 1977

Harrier II introduced 1985.

Oh, my bad thanks. Though I think my point still applies. STOVL is useful enough that they kept the Harrier around in multiple incarnations, since 69.