Place a Large Cargo container and set it at a of height 40 meters and name it box1.

place a second box at zero height and name it box2.
in one of the init lines put box1 attachto [box2]

Last place a vehicle directly under box1.

when the mission is previewed you see box one suspended in the air over the truck a few seconds later the truck is hit by the invisible falling physics. The visual box remains in the air.