A proposed Learjet 45 FAA airworthiness directive is prompted by reports of non-conforming windshield supports (coupe rails). It would require a general visual inspection to detect gouging and scratches and to determine if a radius has been removed; an ultrasound inspection to measure the dimensions of the lower coupe rails; an eddy current inspection to detect cracks of the lower coupe rails; replacement of the lower coupe rails if necessary; and revision of the maintenance or inspection program, as applicable. Failure could result in uncontrolled cabin depressurization and compromise the capability of the windshield to withstand a bird strike.