Final answer:
The upper limits of Class G airspace are defined by the floor of Class E airspace or other designated areas and is overseen by aviation authorities like the FAA. The FAA regulates aircraft separation to maintain safety, requiring specific distances between planes both horizontally and vertically.
Step-by-step explanation:
The upper limits of Class G airspace, which is uncontrolled airspace not covered by any other class of airspace, are typically determined by the floor of Class E airspace, which starts at either 700 or 1,200 feet above ground level (AGL), or by the airspace designations up to, but not including 14,500 feet unless designated otherwise. Each country may define this differently, depending on their specific regulations and the surrounding airspace constructs. However, when discussing the avoidance of in-air collisions within regulated airspace such as that around commercial airliners, the Federal Aviation Administration (FAA) plays a crucial role.
Commercial airliners are subject to FAA regulations to ensure safety in the skies. To prevent collisions, each aircraft must adhere to minimum separation standards which include maintaining a distance of five miles from another plane flying at the same altitude and an altitude difference of 2,000 feet above or below another aircraft. This separation decreases to 1,000 feet if the altitude is below 29,000 feet. The careful control and regulation of these distances, akin to how electrons are restricted in quantum mechanics, allow for the safe and efficient movement of numerous planes in the skies.