"The American airplane lands in this German city."
Translation:Az amerikai repülőgép leszáll ebben a német városban.
I translated the end of this as "...ebben a német városba" which was rejected. I was assuming that the plane is entering the city (from above) as it lands, so I thought -ba would be the right choice. I guess the implication here is that the plane is already in the city as it lands? I'm not even sure what difference it makes.
Rereading my comment (that you responded to), I see the error in my translation, which was that I wrote "ebBEN a német városBA." So they don't even have the same suffix, and they need to match. It should have been "ebbe a német városba," or else both of them should have been -ben/-ban endings.
I think both can make sense given the context. If the point is that the plane is descending into the German city in a way that implies that the sky is not part of the city, but that they are coming into the city by landing there, then I would use the -ba/-be ending. But if the speaker were talking about the landing as something that is taking place within the city (ie, the sky above is part of the city), then you would use -ban/-ben.
(I didn't check into this to be absolutely sure, it's just what makes sense to me given what I've learned. So if this isn't right, I hope someone will speak up.)