Can I use a Priority Mail Express box to ship out regular Priority Mail if I cross out the word "Express"?

Here at Panda we strongly advice against doing this. Your label should match whatever box you're using.

If you ship via Priority Mail in a Priority Mail Express box that has "Expressed" crossed out, you'll still be charged for the Express rate, because that service cost more.

Crossing off words or pictures on boxes should be done when reusing boxes that once had a Hazardous, Restricted, or Banned item in it. The post office will assume whatever markings are on the box indicates what is in the box.

If the box says "Airbags", then they believe it is Airbags. Which is banned from shipping, and your package wont ship.