Aerial Migration (4e Feat)
From D&D Wiki
Avern Alertness [Avern]
You gain overland flight.
Benefit: You gain overland flight equal to your speed. If you have flown for a total of 4 hours or more without taking an extended rest, you may not fly until you take an extended rest.
Special: At 21st level and above your overland flight is equal to your speed plus your Wisdom modifier, and you may fly for up to 24 hours before taking an extended rest.