Do you think anyone ever actually hit a plane with one of these things?
Why would they have even tried? That would be much more useful against soft-skinned or lightly armoured vehicles, or as an anti-infantry weapon against fighting positions or suspected sniper positions, than it would ever have been in its intended use.
Yes. We tested it ingame under ideal conditions. Some observations:
1. The low speed of the rocket makes it very hard to hit planes that are not flying directly towards you and very low.
2. The rockets do not do a lot of damage by themselves and the spread means that hitting planes with a lot of rockets at the same time is a game of chance. Generally speaking, you need 2-3 good hits (meaning a salvo right to the face) to reliable disable a plane.
3. The smoke trails of the rockets give away your position immediately.
4. It takes longer to reload than for example a Panzerschreck.
So yeah, it is useless against planes, but a fun meme kind of weapon nonetheless. You can also rape apcs with it and massed infantry, although not if they are in the open and you are on the same level, chances are the rockets will miss. They have very little splash damage.