EDITORIAL. The Priority Letter ADs against 172R and 182S mufflers is just the latest of a string of highly-publicized Airworthiness Directives against the new Cessna Skyhawks and Skylanes. Previous ADs and Service Bulletins required inspection for missing rivets in the forward door post structure, and modifying the Skyhawk engine cowling to prevent interference. Why this rash of glitches, and what does it mean? We think there are at least three important lessons here.