Aircraft with bleed air rain removal systems, such as Cessna Citation and Learjet, need to have their windshields treated to help disipate the rain. Repcom rain repellant was the recommended product, but it is no longer available.
Rain‑X® is manufactured by the same company and it is the same formulation. While not FAA approved, it works well in dispersing water on the windshield.
*Not Recomended for acrylic sheet products, such as, windshields or windows on small general aviation aircraft.
Rain‑X® Original Glass Treatment dramatically improves wet weather driving or flying visibility. Simply apply the treatment to exterior glass and watch the raindrops fly off your windshield while driving. Rain‑X helps improve visibility by repelling rain, sleet and snow.
I have used this product for years, bit not on my plane. It performed as promised. It even withstood a Midwest thunderstorm at 70 mph. Recommended.
Sent the wrong product then had the nerve to try and charge me for return shipping after I complained that was their error