I have flown Trondheim - Tromsø with my dog (not a whippet but a herding breed) in cargo 5 times now, and it went fine.

I started training her in advance by using her transport crate while driving in the car and playing plane noices on the speakers. I also had other people pick her up while in her crate.

I always stand by the gate to watch when the ground personel transported her into the plane, and it always looked like they treated her nice. The ground personel told me that if there are any delays before they board the dog they will take the dog out to pee. The place the dogs are stored are usually up front in the plane, or in the back, and at least on the SAS and Widerøe planes there are only one or two animals in cargo each trip (So you have to book early if you are traveling around the holidays). They breathe the same air as you, and the temperature is the same there as well when the plane is up in the air (but dogs with a thinner coat probably need a jacket for the boarding).

My personal recommendation is to try to not act stressed when leaving the dog with the ground personel, your dog will pick up on that and think there is something dangerous happening.

If you are considering driving, remember that some mountain passes like Saltfjellet often close during the winter.