With the newly updated AC 91-57, enter 91-57A, our FAA has pressed a clarification of the height restrictions for model aircraft pilots. This impacts R/C Scale aerobatic competition, higher altitude soaring, and much of the safety margin in pattern flying.
Most of the text is a re-presentation of the original Advisory Circular relating to Public Law 112-95, Section 336. However, section (e) now includes the statement:
“Model aircraft operators should follow best practices including limiting operations to 400 feet above ground level (AGL). ”
This is an “Advisory Circular” and not a law but draws a clear line in the sand, or virtual ceiling in the air, at “400 feet” for RC hobbies.