The Bf 109H was intended to be a high-altitude fighter, developed from the F-series.

Some sources point to limited use of the K-14, intended as high-altitude heavy fighter.

The KF-1 started as a proposed "high-altitude fighter" designated K-3.

Petlyakov was tasked with designing a high-altitude fighter, which he successfully accomplished.

Quote: "The Vampire had been conceived during the war as a high-altitude fighter..."

By early 1943, increased Allied bombing raids over Italy had showed that there was no suitable high-altitude fighter to deal with them effectively.

By this time there was little demand for a high-altitude fighter and the project was canceled with only a single aircraft built.

The U7 was a high-altitude fighter, easily identified by the compressor air intakes on either side of the cowling.

The P-39 was from that point forward unable to compete in the European Theater against high-altitude German fighters.

Also, the single-stage, single-speed supercharger meant that the P-40 could not compete with contemporary designs as a high-altitude fighter.