Place the waypoints for the enemy groups. Give groupnames by adding the following code in the leader's init:
groupAlpha = group this;
Name the heli "blackhawk".
Next, have a script or trigger activate a few seconds after the mission starts (trigger: timeout 5-5-5, condition: true)
On activation:
[groupAlpha, 1] setWaypointPosition [getPos blackhawk, 0]