Okay, now the advanced fighters could escort a bombing mission. So I am not sure, if its really a bug or I just clicked the wrong area (bombing in A and escorting in B).
But here's another bug - will occur really rare:
Spain is on side of the axis and attacked allied forces in West France. Spanish forces won, but the territory West France will not be colored the right way (bright blue). Save game is attached.0_1539451273735_spain cannot conquer West France.tsvg