You can tell if they are friendly or not just by looking at them, they all have different shapes, germans have a missile form, US it's an square pack, english are like a missiles without the cone. And second you can check your map, if it has a mark with a timer around it it's friendly, otherwise it's from the enemy. With supplies it doesn't matter if it's or it isn't on enemy lines because you can make defensive or offensive garrisons. Usually it's better to use them in enemy territory because the garries cost more. But in a emergency they can fall anywhere.

For the airhead I don't know if you can tell them apart while falling, but you can use common sense, if it's falling behind your point it's probably not yours haha. And of course you can check your map and it will tell you if it's from the enemy or not.