ΔE 6.8, close: similar, with a visible difference side by side. US Interior Yellow is a little darker than Flak Gun Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). US Interior Yellow is a little darker than Flak Gun Yellow.
The same difference applies the other way round: Flak Gun Yellow is a little lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Flak Gun Yellow on the colour wheel See US Interior Yellow on the colour wheel
All matches: Flak Gun Yellow equivalents · US Interior Yellow equivalents