An American Airlines flight out of Sacramento was canceled over the weekend because of a stowaway that made both passengers and crew members uncomfortable. That stowaway? A scorpion.

The plane most likely picked up passenger number 126 during its previous stop in Phoenix, and the crew learned about it while passengers for the flight from Sacramento to Chicago were preparing to board, the Sacramento Bee reports.

The airline ultimately decided to cancel the flight, booking passengers on other, presumably scorpion-free, flights instead.

“The flight was canceled because we want passengers and crews to feel comfortable,” an airline spokeswoman told the Bee.

While scorpion stings from species native to North America are generally not life-threatening, they can be very painful.

The airline didn’t know whether the scorpion was still on the plane, or whether it had any friends, so the aircraft was sent to a maintenance facility for fumigation to ensure that it’s bug-free before making any more trips.

American Airlines doesn’t allow scorpions on its planes in any official capacity, even if they’re pets. Only cats and dogs are allowed in the cabin or in the cargo hold or the cabin of planes.

Arachnids can cause chaos on planes whether they’re allowed or not, though.

• A pet tarantula escaped its carrier on a Delta flight in 2015, delaying takeoff until humans could find it.

• A scorpion stung a woman on an Alaska Airlines flight from Los Angeles to Portland, OR, while the plane was taxiing, and returned to the gate. She received medical attention, and the crew searched overhead bins for more scorpions.

• Tarantulas on an Air Transat flight might have been smuggled pets or stowaways, but they were an “aggressive” non-venomous species that can grow up to eight inches long.

• After what was already a bad week for United after its infamous passenger-dragging incident, a scorpion fell on a passenger’s head and stung him during a flight from Houston to Calgary.

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