But cats? Live cats? Tucked inside carry-ons? It's happened before, and now it's happened again.
On Friday morning at Norfolk International Airport in Virginia, a feline was discovered inside a passenger's carry-on bag during a security screening.
The Transportation Security Administration released an X-ray photo of the poor pet cat in its official Twitter feed.
The tweet came with one of the TSA usual puns: "Attention pet owners: Please do not send your pet through the X-ray unit. Cat-astrophic mistake!"
How to properly board your small pet
How did all of this even come to happen?
"This was a case where the passenger was traveling with their pet," LIsa Farbstein, a spokesperson for the TSA, told CNN Travel by email on Friday afternoon. "They knew the pet was in a carry-on bag, because this was a pet travel case/container.
"It appears that the individual either did not know to remove the pet from the carry-on travel case before going through the checkpoint, or forgot to do so," she said.
"When that happens, they have to start all over again, meaning that the passenger and the cat have to start over at the checkpoint.
"The passenger needs to remove the pet from a carry case and carry it through the walk-through metal detector or walk the pet through the metal detector on a leash. This is typical of how people travel with small dogs. In the case of a cat, if there is no leash, we strongly recommend that the passenger requests screening in a private screening room."
She said the reason is because "cats tend to be more skittish than dogs and might wiggle, scratch, bite and jump down and try to run away."