Coatings for today's ordinary commercial aircraft must cope with extreme service conditions. They may take off from searing desert heat, climb within minutes to a height of ten kilometres where temperatures fall to -55°C and where UV exposure includes high levels of short-wavelength UV (UVB), most of which is blocked by the atmosphere at ground level. Then the aircraft lands...perhaps in sunshine again, perhaps in a snowstorm.
These rapid changes, combined with air turbulence, structural flexing and changing air pressure, place coatings under severe stress. Landing a very cold aircraft in humid conditions can also produce extensive moisture condensation in unpressurised areas.
In addition to these environmental abuses, paints will be exposed from time to time to aggressive chemicals including fuel, de-icers, cleaning chemicals and Skydrol, an aviation hydraulic fluid noted for its destructive properties. Regular washing is required to remove accumulated dirt and potentially corrosive salts when operating in maritime areas.