It's not a permanent welded-in plug, rather it's a door-shaped panel that is secured in using the fastenings where the door would be fastened. That's why you ca

It's not a permanent welded-in plug, rather it's a door-shaped panel that is secured in using the fastenings where the door would be fastened. That's why you can see the outline. The one thing an airline likes less than carrying extra weight is not being able to change their minds later :) Or rather, for the option to be available for whoever they sell the plane to after they're done with it.