As someone who renders airplanes every day, here's my feedback:
- No need for a LayeredMtl approach unless the original paint has metallic flakes which is not the case for most airlines. A simple CoronaMtl will be fine. Historically, airplane paint was applied in two layers some years ago, a base paint and a clear coat. Today's paints are mixing both and only one paint layer is applied in order to save time and weight (which saves money in the end).
- If you need to use separate Materials for the base paint and the clear coat, use a Fresnel mask instead of Perpendicular/Parallel.
- Your clear coat material is too blurry imo. Unless the airplane hasn't been cleaned for two years - which really doesn't happen since commercial airliners get cleaned every two weeks at least - the reflections are almost perfectly sharp. A glossiness value of 0.98-0.99 will do.
- IOR of 1.52 - 1.6 will work fine.
- Since airplanes are huge it's good to add some noise maps for Reflection and Glossiness, only slightly visible.
- Add two levels of bump, one for the larger panels so there's slight large scale curvature and one for small bumps, similar to how a car paint looks.
Attaching some examples for reference.
