All of our products are no more than 3.4 fluid ounces and TSA-approved for carry-on. We always recommend keeping the Mist in your carry-on bag to ensure that the live AOB (Ammonia-Oxidizing Bacteria) are not exposed to the extreme temperatures of the checked-bag cargo hold.
Don't worry about x-ray machines. The AOB have a very small genome, so they make a very small target for the x-rays. Diagnostic doses of x-rays have no discernible effects on bacteria or their environment.
Other Mother Dirt products can go in your checked bag. If they freeze and then thaw, they are still okay to use.
Again, extreme temperatures will affect the little guys in the AO+ Restorative Mist, so better to play it safe and bring them aboard. To be super specific, the Mist can withstand 72 hours at 100 degrees Fahrenheit. It would require hours at well-over 110 degrees to degrade the AOB. Freezing temperatures are always bad!