Krister, you are surely mistaken by picture of flying falcon
Black moustache is really contrasting, but the lower appendix is narrow and pointed, cap isn't as black as it seems in the photo ( pay attention to the same individual perching on a vire on another page ), beige undertail isn't always a proper pattern for determination. In this case, for my opinion, the best pattern distinguishing F. subbuteo juv and F. vespertinus juv is well visible on the flying falcon - distinct dark trailing edge of wing underparts.
