The category "<ship_class-not_creatable-pl>" can be expressed as follows:
aegises
aoe-6s
assad corvettes
assads
attack boat flotillas
cg-65s
chosins
civilian freighters
civilian merchants
civilian tankers
corvettes
csg-1s
cvn-68s
dd-963s
ddg-72s
fishing boats
freighters
harpers ferries
hudongs
landing craft utilities
landing crafts air cushioned
lcacs
lcus
lhd-1s
los angeles's
lpd-17s
lsd-49s
lupo frigates
lupoes
mahans
mcm-1s
mcs-12s
merchants
mhc-51s
missile attack boats
missile boat flotillas
nimitzes
opfor submarines
opfor subs
pgms
rms's
spruances
ssn-688s
tankers
ticonderogas
trawlers
wasps