These aircraft were in WIP for a long time (Months or even for a year), I just lost inspiration on these airplanes.

BT.III | 65-70% finished
Was supposed to be a WW1 biplane bomber.

M-21E-3 | 40-45% finished
Was supposed to be a WW2 interceptor.

F10G-4B Thunderkraken 80-85% finished
Was supposed to be a fictional naval fighter created by Republic Aviation, the same company who created the P-47 Thunderbolt.

Unknown Aircraft | 35-40% finished
Was supposed to be a fast spy aircraft.