Maximum Authorized Altitude (MAA)
A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment. It is the highest altitude on a Federal airway, jet route, area navigation low or high route, or other direct route for which an MEA is designated in 14 CFR Part 95 at which adequate reception of navigation aid signals is assured. MAYDAY-The international radiotelephony distress signal. When repeated three times, it indicates imminent and grave danger and that immediate assistance is requested.