[stansdds]

You can simulate engine problems with AI aircraft by not giving them enough fuel to complete the mission. Generally speaking, AI will turn back when they reach the point at which they have just enough fuel to get them back to their base. So if a mission is going to use 50% of an aircraft's fuel capacitiy, setting one or two AI to 25% will see them fall out of formation and return to base during the outbound leg of the mission.