Hubby and I adopted a senior GSD in 2008. He was around 82 lbs at the time. The rescue would not ship him without owner's presence so hubby flew to Los Angeles to pick him up. It was a 4 hr flight.
The largest kennel he was able to find (he was only in L.A. for a few hours) was 30" high. Our new GSD could barely stand in it (with head hanging low). The airline (I believe it was American Airline and the dog was traveling as cargo) personnel almost turned them away because his crate was too small, the personnel thought the dog looked uncomfortable. At the last second, our new GSD decided to lay down and curled into a ball. That changed the personnel's mind.
They were very lucky, so just be aware that if your crate was too small, you do run the risk of not being able to board with your dog.