Hi!
With the way that the game looks in the images, it appears to be the old update. In the old update, G1 and 2 could fly on Training. However, you have to be G3 to be able to fly on the Expert server.
What can happen is that a pilot on Expert or Training collects violations, by over-speeding for example. During his flight, the violations change his Grade. But he’s still flying. After closing or even pausing his flight, he will be denied access.
Hope this clarifies.
If this is indeed an old picture, as Conner suggests, then this could happen because the rules were different then.
That is definitely the Training server. If you see a grade 1 person flying around the place it is definitely NOT an expert server. There must be a mistake in this YouTube video you were watching.