Airspace

"Airspace" refers broadly to the areas in which air and spacecraft may travel. In the far future, the restrictions and divisions of airspace have been extended from the way they currently exist in the 21st century. Provisions have been made to include divisions between different classes of planetside airspace, different orbital altitudes, and the existence of artificial and natural satellites around a planet. The altitude and distance values listed below are for the space and altitudes surrounding Earth. Other planets almost universally use the same system, although the altitudes and restrictions are adjusted for the atmospheric density and population centers of the other planets.

Planetside Airspace
On Earth and most other populated planets, the airspace classifications used in the 21st century generally apply. Airspace is divided into 5 different classes which are considered "Planetary." Each of these is given a letter value, with decreasing restrictions with alphabetical order. These letter values are always referred to by their NATO Phonetic Alphabet pronunciations.

Class E (Echo)
Class E Airspace is uncontrolled airspace. This includes airspace close to the ground in unpopulated areas, at least ten kilometers from a controlled spaceports. Pilots in Class E Airspace do not need to communicate with Traffic Controllers, but are also responsible for their own navigation.

Class D (Delta)
Class D Airspace is for small controlled spaceports and airports. Generally, Class D Airspace is limited to the 20 - 30 km radius surrounding the port, and rarely more than 1000 meters above the port. Pilots entering this airspace must communicate with controllers at the port before entering or transiting the airspace.

Class C (Charlie)
Class C Airspace is for larger city ports and their surrounding territory. These are similar to Class D Airspace, except their airspace often extends wider and higher, while not always extending to the ground (except in a smaller radius around the airport). Pilots must communicate with the controller at the port before entering or transiting the airspace, but may often choose to avoid the heavy traffic.

Class B (Bravo)
Class B Airspace is for the area surrounding major spaceports and the areas surrounding their primary approach paths. These sections of airspace are often ordered like an inverted cake, with small-radius sections at lower altitudes and large-radius sections at higher altitudes. These control large portions of airspace in order to avoid traffic conflicts in the busier ports, and any pilot entering a Class B area is required to be operating an craft with certain minimal navigational equipment while maintaining constant contact with controllers before entering the airspace. Some Class B Ports do not allow non-spaceworthy aircraft inside their territory, or else have speed restrictions for craft entering their area. Some Class B extends incredibly high into the atmosphere to account for vertically-launching spacecraft. Oftentimes, commonly used approach paths will be included in the port's Class B blockout.

Transitional Airspace
Most planets have a high-altitude section of airspace which is reserved for high-speed air and spacecraft. These are generally divided into two different altitude blocks to account for distinctions between high-speed aircraft and spacecraft operating at lower altitudes.

Class A (Alpha)
Class A Airspace accounts for the airspace between 5500 meters and 30 kilometers. This is the highest altitude at which an ATM-O or ATM-E aircraft may legally operate. All pilots opperating in this airspace must be on a filed flight plan and must be communicating with air traffic controllers constantly. This airspace is usually controlled from a central traffic control center (or several regional centers) to help aircraft and spacecraft avoid conflict with craft making Rapid Descent Suborbital Approach Profile (RaDSAP) Approaches. This classification does not exist on planets with little or no atmosphere.

Class S (Sierra)
Class S Airspace Marks the transition to "Space" in the legal sense. This is an altitude range from 30 km to 200 km. Rules are the same as Class A Airspace, although very few craft spend much time in this zone. The air density is too high to maintain a stable orbit but too low to maintain lift-based flight. This is also the portion of airspace reserved for RaDSAP Approaches, which get priority navigation in Class S Airspace. On planets with no atmosphere, class S will often extend much closer to the ground.

Orbital Airspace
Orbital Airspace is divided into sections based on altitude. Generally, every planet has at least 3 Orbits: Low, Geostationary, and High Orbit. Additional Orbits may exist on larger or more populous planets to allow for the control of higher traffic areas. Additionally, every artificial and natural satellite has a controlled area around it. Stations will often control an area of 100km around them, while natural satellites will implement altitude layers as described above.

Orbital Naming Conventions
Generally, orbits are named following the convention of the letters F through R, though the latter letters are rarely used. Low-Earth Orbit, for example, is Orbital Zone (F)oxtrot.

Orbital Zone (F)oxtrot
Low-Earth, where most pilots prepare their transitions into the atmosphere. Due to satellites here, this space is controlled very carefully, and pilots will spend very little time here. From 200KM to 2000KM

Orbital Zone (G)olf
Medium-Earth, the common placement for “Parking Orbits”, this otherwise quiet region of orbital control is where many ships will “Park” for repairs, or when they send shuttles to the planet if they aren’t atmosphere-capable. From 2000KM to 35000KM

Orbital Zone (H)otel
Geostationary Orbit, a relatively small range from 35000KM to 45000KM where many stations are built, often placed equally around the orbit to allow a station to be fixed over every major population center. Traffic here is heavy, but the strain is mitigated by the addition of station-control, where Orbital Control can Hand-Off Pilots heading within 100KM of a Station.

Orbital Zone (I)ndia
Intra-Lunar Orbit, the Space between geostationary orbit and Lunar Orbit. This space is frequently populated by shipyards and drydocks with their own Controllers, but most ships who don’t have business here are just passing through. From 45000KM to 380000KM.

Orbital Zone (J)uliet

Lunar Orbit, the altitude between 380000KM and 450000KM. Divided into Center, Approach, and Departure, for those passing through the orbital zone, entering Lunar Orbit, or leaving Lunar Orbit, respectively.

Orbital Zone (K)ilo
Post-Lunar Orbit, the area of Earth Orbit beyond the Moon, is the highest level of orbit around Earth. It is sparsely populated and generally only used as a transitional zone. Legally, it is any stable orbit above 450000km.