Flak36 AA confusion

Hi all.
New to the forum and only 3mp BG battles under my belt.

My question is regarding flak36AA use. We got stuck yesterday whilst trying to figure out if my gun could actually shoot in AA role. Med gun on long range gives a not possible "-" on the area fire table. Is this correct or have we missed something obvious?
My 37mm plus some pintle mgs drove off the plane but I was desperate to let the 88 get involved.

All advice very welcome.
Cheers

No, it is designed to fire at high altitude flying aircraft, not the sort that would be attacking troops on the ground which are to low and fast.

Thanks, Phil.
That's what we imagined.

In Westwall supplement Panzer Brigade Additional Fire Support, the Army Battery roll of 5 gives the option of 2 x 210mm L35 howitzers. Is this a typo? 210mm L31 or 240mm L35?