At first I couldn't quite find the actual playing area and was flying around the building instead of into the entrance to its inner section... That clearly needs some better indication (and, as you already mentioned, some limits to keep the player within the level).
The packages actually seem to be quite heavy, so the rubber band might break when the package gets stuck at some corner and needs some careful maneuvering around. Especially when turning downwards where the player's drone goes much faster than the package (and then might get crushed below it). :)
The drone motor buzz sounds quite realistic, especially when you try to lift up with a package in tow.
Nice touch there were several BGM tracks!