So as far as I understand 'to flee' is the verb, derivative noun from it is 'a flight' (as the process of running away), but what are the people who flee called? (And I don't mean cowards and other words of this kind.)
How about fugitive? Here is how Encyclopédie Universelle defines that term:
a person who is fleeing, from prosecution, intolerable circumstances, etc.; a runaway: a fugitive from justice; a fugitive from a dictatorial regime.
What about runner? The term is frequently used in popular media to identify one that flees. The website subzin lists at least 30 instances of the phrase “We have a runner.”
Flee is synonymous with hasten, also a verb. It is derived from the Old French word 'haste' a noun which means: "Energetic speed in motion or action, as from eagerness, fear, urgency of circumstances, etc." From that a person who hastens(flees) is a (hastener). Source: The New Century Dictionary of the English Language, D.Appleton-Century Co., New York-London, 1944, p.717