ΔE 7.6, close: similar, with a visible difference side by side. USAF Tan is a little darker, warmer than RAL 1039 F9 Sandbeige.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). USAF Tan is a little darker, warmer than RAL 1039 F9 Sandbeige.
The same difference applies the other way round: RAL 1039 F9 Sandbeige is a little lighter, cooler.
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 RAL 1039 F9 Sandbeige on the colour wheel See USAF Tan on the colour wheel
All matches: RAL 1039 F9 Sandbeige equivalents · USAF Tan equivalents