[2021] when were the first jets added

Examples of jest being in the game "since the beginning" (Open Beta Tests):

Me 163


Me 262A-1a

Post war but WW2 designed (added in 1.33):

F-80C Shooting Star


Yak-17


Vampire FB 5

Post War jets (added in 1.35):

F-86F-25 Sabre


F-86F-2 Sabre


MiG-15

Few others added between (1.27-1.31)