I just checked the app and I noticed the Expert Server is a mere 1% higher than the Training Server.
So I went through them both and the Training Server looked much more crowded than the Expert. So, I went more into detail and added all the available flights in each from their lists and I again got the same result, which is in sharp contrast to the Server Load the app shows!
Training Server: 14+22+18+12+22+7+4x5+3x4+8x3+19x2+(80~90)x1=269
Expert Server: 15+15+9+6+4+4x3+10x2+48=129