Wingmen will not drop bombs

[ZiggyM]

Hello.
What is the trick to get wingmen to drop their bombs?   I had them in formation over the target, hit the "attack nearest ground" and they broke formation and didn't drop any bombs.  On the way home we came across a 2-seater, 5 on 1, so I hit the 'attack nearest air' and they didn't attack.  They were flying 'high cover' as I attacked but never fired a shot or dove to attack.

What is the trick to get them to engage?

 

Thank you.