I think zahavasdad et al. are correct and the same thing is written on a kikar shabat article, that the passenger being a Cohen is the reason, the plane route was above Gush Dan cemetery, and that Rabbi Elyashiv paskened the plastic bag is OK. You can look up the article on kikarhashabat.
I heard that problems with cemeteries depend on the height and I recall being told it is a possible problem only with hot-air balloons and other low altitude sports, or, for commercial flights, only close to takeoff and landing, which looks like was the case here.