There was something recently introduced that encourages formation flying. Two patches ago HTC introduced the ability in a .command to keep formation with a target you designate as a wingman (.wingman XXX)
That is a fantastic addition!!! It allows specifically bomber formations to stay in formation even when under attack. It is not perfect however (nor should it be) and one needs to keep this in mind.
The formation leader CAN NOT fly at 100% or near 100% throttle and expect the rest of the group to maintain formation with this command. This also could aleviate the groups that think bomber groups should not fly at top speed
Second If the formation leader does maintain a reasonable speed to maintain his group it is very important he doesnt make any maneuvers whilst the enemy is attacking. Any movement he makes causes anyone attached to him to correct. This can include accidental rudder inputs while gunning using a twisty stick.
Strangely I have heard almost nothing about this fantastic feature added, and most every bomber mission thus far (including strat raids) does not seem to take advantage, and even if they try it, the idiot flight leader insists on flying at something like 95% manifold and making course corrections with no regard to enemy activity.
In short HTC just added something to encourage flying as a unit...and it unbelievably does not appear to be used often.