the first upgrade for planes has been broken since the start of the game. it actually makes your plane worse overall because some smart person changed the signals. also shown are wt signals to see where they copy pasted from.
only lift efficiency is correct.
i suggest to leave as it is because i want to save silver, i’m not getting enough even with premium. right now there is no advantage in wasting silver to get all the upgrades.
I have most of my planes on a very low level, there is no reason to use silver on upgrades if you are good enough.