If you are wingman, engage autopilot briefly to get permit to take off.
If are group leader, leave the autopilot engaged until first way point for
AI wingman follow you/accept this formation commands.

Instead use this second procedure, Desastersoft discover that:

Taxi to the runway.
Ask for conditions for take off (TAB -> 7 -> 3)
Ask for take off permission (TAB -> 7 -> 6) *
Take off.
After take off go into a traffic pattern to the right side and keep on circling until aircrafts number 2, 3 and 4 of your flight are in the air.
If you stay in the traffic pattern, the AI aircrafts can still see you and will join you, as if auto-pilot is used.

* The tower response (for takeoff/landing) is always negatives because script message for this are inverted, so ignore an go.
TF promised revise this for Patch 5.0 (2015).

Sokol1

Nice tip...laborious but perhaps one for the realism fans

H

I still fly the original Eu release of the game, most times that is. Since I don't have this issue it must have been a patch introduced bug at some point. I can go right, left, or straight but they will always follow on take off and in route, no auto pilot needed or used. Patches rushed out the door really screwed up the game back then.

Confirmed.
Now taxiing&take-off differs not much from a 'standard' procedure

I fly Desastersoft missions and thought they'd tweaked the AI command features, so it's good to know these tips are effective in other missions as well.

Does this method work when starting from the runway with engine running? I tried this method in one of the TF dynamic missions, but the ai took off and then returned to base.