[stndbfrgrn]

Hello!
As far as I know, the only way to get your wingmen to attack is to have all the radio options under "air targets" in bright red. This seems to be somehow tied to the flight formation you selected, which should be set to "close", therefore allowing your mates to visually acquire the targets, but I have no proof: it's possible that they won't attack even when an enemy aircraft is on their nose, or shooting at them, or that they will attack without any order.
So, set your formation to "close" and wait for all the options to be bright red if you want to issue the attack order. It's hit and miss, be prepared for more frustration.