Most in-cabin rules require pets to be small enough to fit in a carrier under a seat, excluding many snub-nosed dogs. The following major domestic airlines DO NOT allow flying pugs or other snub-nosed breeds at any time: United Airlines American Airlines Delta Alaska Air. Airlines like Southwest and Allegiant, which don’t have specific restrictions but will only fly pets in-cabin. Snub-nosed breeds are susceptible to respiratory difficulties during air travel due to their unique anatomy. As the plane takes off and gains altitude, air pressure decreases, and oxygen levels drop, exacerbating breathing difficulties in these breeds. Conversely, air pressure increases during landing, causing discomfort to snub-nosed breeds. It's crucial to keep your pet calm and comfortable, by ensuring they are crate trained and ensure that they are well-hydrated throughout the flight. It's important to consult with your veterinarian and airline to determine whether air travel is safe for your pet and what steps you can take to ensure their comfort and safety during the journey.