Yep, it seems we have a serious problem when DAR is off and no more enemy info is displayed on screen.
1 - Enemy activity bars over friendly territory should be displayed always.
2 - Enemy activity bars over enemy territory shouln't be displayed unless friendly aircrafts are in that sectors.
3 - Friendly planes should be displayed always, it is supposed they transmit their current pos using radio.
4 - When DAR is lost, we can get enemy pos information using "reconaisance" aircrafts. This should be difficult to implement because it implies to determine if the friendly aircraft can see the bogies or not.
There is an easier, but less precise way to implement this, and this is as follows.
When a friendly plane sees an enemy, he can press a key and its dot over the map changes to a color different than green, once he lost sigh of enemies, he press another key and its dot appears green again. The color selected to indicate that a plane have seen enemies depends on the number of times that pilot press the "enemy vis" key. So, it is acumulative. This should be usefull to indicate the number of enemies that pilot is seeing. For example, one press render its dot yellow and indicates 1 - 3 enemiples, two presses draw the dot light-orange and indicates 3 - 6 planes and a third key press draws the plot dark orange and inidicates more than 6 bandits. Each "no enemy vis" key press subtrack one to the counter, so, if a pilot has presed three times the "enemy vis", he should press thre times "no enemy vis" to have a "green" dot again on the map.