Air support issue (PzC Market Garden as Allies)

[skc007]

Wargamers,

In JTS PzB "Market Garden" as Allies I am having a frustrating issue. 
I just cannot seem to be able to use much of my available air power. Sometimes it works but often not, esp high level bombers. I keep on getting "Unspotted"  or a "cannot be spotted by subordinate unit message" (even though ground Units are right next to the enemy hex and spotted highlight shows spotted.)

I suspect there need to be Units designated specifically to the air arm but there seems to be little help in the manuals etc.
Any help appreciated. (Need all help I can get, as am losing with only 30 moves left!):

Thanks in advance.