While the Parking Attendant may not really be the highest priority, there are some achievements that could use a higher levels. Just of the top of my heat:
- Number of destinations flown > 500, for example 600, 700
- Company value > 350 bn, for example, 500, 750, 1 trillion (ZombieSlayer would already have 500 and 750, Herman would have 500)
- Aircraft in operation > 1500
I am sure there are more