Extraterrestrial Airspace is a concept that dictates exactly where a planet's authoritys jusristiction begins and ends, and where a planet can truely say "you are trespassing". This can be used to help justify making advances or outposts in an unclaimed solar system, near a planet controlled by other forces. this law is not applicable in solar systems completely controlled by factions, as thet claim total dominance over the system, not just their planets airspace. most civilization will, unfortunatey, diregard this, and even claim whole tracts of space, due to their holdings in one planet.