MSL Regulation
MSL means mean sea level.
Also defined in 2 more sources
Mean sea level. When the letters MSL are used with an altitude, it means that the altitude is measured from mean, or average, sea level.
Guidance: Aviation Maintenance Technician Handbook — Airframe, p. G-23
See mean sea level.
Guidance: Pilot's Handbook of Aeronautical Knowledge, p. G-20