Airline Level explained: Progression thru the levels is accomplished by tracking game activity. The primary measure of game activity is Starting Routes and Repairing Damage. I am currently at level 48 and 18% of the way to level 49.
Airline Manager Level
Once I reach level 50 I will unlock the Achievement Badge for Level 50. Once at Level 100 I will receive Achievement badge for level 100. Currently there are no additional Level Badges beyond Level 100.