I've just picked up a copy of this after having it on the wishlist for years.
Reading through the rulebook it mentions that the SO cost (or bonus) for each aircraft is on the card near the years in service. My eyesight must be getting bad as I cannot find this information on any of the cards.
Has the SO cost been removed from the cards in later reprints?
I believe some of the aircraft have a "standard" rate or baseline rate and are absent from the cards for some reason. It should be referenced somewhere in the rulebook. Sorry I can't help more, but the rulebook is out of reach. Reference the photo below (especially Alpo and Tigger):
Precisely. If there's no SO cost listed, assume the SO cost is 0.
Note there are aircraft for which you gain SO points (A-7 and AV-8B) as well as the ones which cost SO points (F/A-18E, F/A-18F, EA-18G, and F-35B/C). If there's any doubt, the rulebook has the aircraft listed starting at page 17. In the Special Rules section for the aircraft, it will include the SO cost/gain if any.