Flights that leave at the crack of dawn tend to be more reasonably priced than ones later in the day.
If you are hunting in a new area, you might want to arrive before the crack of dawn.
Slang definitions & phrases for crack of dawn
crack of dawn
First light; the start of sunrise (1923+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with crack of dawn
Very early morning, daybreak. For example, I got up at the crack of dawn. The crack in this term alludes either to the suddenness of sunrise or to the small wedge of light appearing as the sun rises over the horizon. Originally the term was usually put as
crack of day.
[ Late 1800s