KingTiger and Vega, there is a problem with the strings to be added to air.ini and plane.properties files, the separators are not correctly read by the game.
KingTiger, try to copy-paste this instead, it should work:
air.ini
MiG-19S air.Mig_19S 1 NOINFO r01 SUMMER
MiG-19SV air.Mig_19SV 1 NOINFO r01 SUMMER
MiG-19P air.Mig_19P 1 NOINFO r01 SUMMER
MiG-19PM air.Mig_19PM 1 NOINFO r01 SUMMER
MiG-19SU air.Mig_19SU 1 NOINFO r01 SUMMER
MiG-19PU air.Mig_19PU 1 NOINFO r01 SUMMER
SM-12 air.SM_12 1 NOINFO r01 SUMMER
SM-12PMU air.SM_12PMU 1 NOINFO r01 SUMMER
F-6 air.F_6 1 NOINFO r01 SUMMER
FT-6 air.FT_6 1 NOINFO r01 SUMMER
plane
MiG-19P MiG-19P Farmer B, 1955
MiG-19S MiG-19S Farmer C, 1956
MiG-19SV MiG-19SV Farmer C, 1956
MiG-19PM MiG-19PM Farmer E, 1957
MiG-19SU MiG-19SU Farmer C, 1956
MiG-19PU MiG-19PU Farmer E, 1956
SM-12 MiG-SM-12PM Farmer S, 1957
SM-12PMU MiG-SM-12PMU Farmer S, 1957
F-6 Shenyang F-6, Farmer C, 1957
FT-6 Shenyang FT-6, Farmer F, 1960