Evidence: https://www.youtube.com/watch?v=_IDIhzPNbm4
The quest ‘From Ground to Air, From Ground to Ground [Cannoneer Advancement]’ has its description incorrect.
while the order is the following:
Defeat the walking monsters (0/50)
Defeat the flying monsters (0/50)
killing walking monsters adds counters to the flying monster counter (shown in the video), killing flying monsters adds to the walking one.