Section I.2.2: Ships and Bases: Flags:

Name of Flag Position* Description
CAN_LAND 7 Ship can land on a planet.
DISABLED 5 Ship is disabled.
INVINCIBLE 1 Ship is invincible.
NAKED 4 Ship's shields are inoperable.
PACIFIST 6 Ship cannot use weapons.
POKEY 3 Ship's warp costs twice as much.
SPEEDY 2 Ship's warp costs nothing.

* Position indicates the character position of the flag in the ST_SHIPFLAGS bit map, from the left.