During the final shot when the camera is zooming out from Orbiting Meadows, the 2 guards are no longer at their post.
Fry opens the sleeve of the Breakfast Club record from both sides.
The mound of earth by the grave disappears when the camera zooms out.
As the Planet Express ship fly's into orbiting meadows the airlock doors open almost at the same time this would cause a lot of oxygen to evacuate as the environment wouldn't be sealed.