An Alert Area on a sectional chart is identified by:
AAn 'A-' prefix (e.g., A-220) with a magenta hatched border indicating high volume of pilot training or unusual aerial activity✓
BA 'W-' prefix with blue hatching
CA 'T-' prefix with dashed gray border
Why →Alert areas are depicted with 'A-' prefixed identifiers and magenta hatched borders similar to MOAs. They indicate locations with high concentrations of pilot training activity or other unusual air operations. Flight is not restricted but heightened vigilance is expected.
The trap →Alert and MOA styling can look similar; the prefix distinguishes them (A- versus MOA name).
Field note →Alert areas tend to blanket flight-training hotspots, central Florida being the classic case. Operating a drone nearby means expecting low-altitude training traffic.
SOURCE → FAA Aeronautical Chart User's GuideCHECKED JUL 16ACS II.A.K3EASY