Andy,

SN10 supports:

T - Turnpoint
L - Landable (safe landing field, shows on Alternates page)
A - Airport (not necessarily landable)
S - Start point
F - Finish Point
M - Point of interest (Mark point?)

These can obviously be used in combinations; Turf, for example, is a
TLASF in my database. OTOH, Luke 2 would be a TA and would not show
up as an alternate.

Kirk
66