After having travelled a few times on a plane with my pup, this is what I've learned...

Make sure the crate has something absorbant like a towel at the bottom. Always carry an extra in case of water spillage, accident, etc.

Don't fill bowls to the brim or there is a risk of messes.

Keep your pup calm. They will kick you off the plane if they are too noisy.

Do not sedate your dog before the ride. This was taken from the Alaska Airlines web site.
Sedation is not advised since the effects of tranquilizers on animals at high altitudes are unpredictable. The decision to prescribe a tranquilizer for your pet should be made by your veterinarian.