1. So when your in the editor you can press show drag and the draggy bits show up red in this feature you pres the button title SMOKE or WIND TUNNEL and smoke would start in front of the plane and the smoke would flow over the aircraft And I know it is possible because of this Watch it to end to see my point

2. When you Fire guns it leaves some smoke like the A-10 Thunderbolt/Warthog
   Like in this vid to see what I am talking about it shows it a 15 secs in

3.The reason is because smoke trailers using missiles have tendency to blow up in maneuvers for example i was recently flying Hyperloop's SU-30 and I tried to put smoke trailers on the wings and than using the thrust vectoring tried to do a cool trick while the smoke was on but the missiles just blew up in the G force so thats why we actual smoke trailers PS the change color part is just for show and would be cool

Here is the Sukhoi

1. When hit by bullets you start to leave a trail of black smoke or white if you are hit in fuel tank (Were you decide to put your fuel) once hit again you start smoking and small pieces start to come off once hit again a major part comes off (Wing, Tail plane, etc) or you explode also at first hit if fuel starts to leak there is a 6/10 chance it will catch fire and if you are hit in the engine they start to smoke black smoke and produce less or no thrust.
   If hit by missile you explode into a fire ball (Like SP bombs but more fire less smoke!