Airspace System

The atmosphere has several areas and levels, here we will know all of them


Controlled Airspace is an airspace of defined dimensions within which air traffic control service is provided in accordance with the airspace classification.


There are 3 services available in controlled airspace:

  • Flight Information Service.
  • Alerting Service.
  • Radar Control Service.


Flight Information Service:

A Flight Information Service (FIS) is a non-radar service provided, either separately or in conjunction with other services, for the purposes of supplying information useful for the safe and efficient conduct of flights. Under a FIS the following conditions apply:

  • Provision of the service includes information about weather, changes of serviceability of facilities, conditions at aerodromes and any other information pertinent to safety.
  • The controller may attempt to identify the flight for monitoring and co-ordinationpurposes only. Such identification does not imply that a radar service is being provided or that the controller will continuously monitor the flight.
  • Pilots must be left in no doubt that they are not receiving a radar service.
  • Controllers are not responsible for separating or sequencing aircraft.



Alerting Service:

An alerting service is provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required.


Radar Control Service:


  • radar control service may be provided to aircraft operating IFR, SVFR or VFR. When providing the service controllers issue instructions to which.
  • pilots of aircraft operating IFR are required to comply.
  • pilots of aircraft operating SVFR or VFR will comply unless they advise the controller otherwise.


Within uncontrolled airspace in the Saudi Arabia, aircraft may operate free of the control of an ATC unit. However all aircraft are required at all times to conduct their activities with regard to the CAA Regulations.
When cruising in uncontrolled airspace, The pilot should monitor UNICOM (122.800)


Quadrantal Rule

When cruising above 3000ft in Uncontrolled airspace, aircraft should comply with the quadrantal rule. The altimeter setting should be 1013.25 only above Transition altitude. And about cruising level betwing 000 – 179 odd and 18 – 359 even. The altitude should be indicated as level only above 13000ft.

Magnetic Track Cruising Level
360° to 089° FL50, 70, 90 etc. up to FL190
090° to 179° FL35, 55, 75 etc. up to FL175
180° to 269° FL40, 60, 80 etc. up to FL180
270° to 359° FL45, 65, 85 etc. up to FL185

Unless otherwise stated, the Transition Altitude is 3000ft. FL35 is only available when the local QNH is greater than 1013mb.




There are 4 types of ATC service available to aircraft outside of controlled airspace:

    • Alerting Service.
    • Flight information Service (Radar).



Alerting Service:

An alerting service is provided to notify appropriate organisations regarding aircraft in need of search and rescue aid, and assist such organisations as required.



Flight information Service:

A Traffic Service is an air traffic radar service in which the controller shall inform the pilot of the bearing, distance and, if known, the level of the conflicting traffic. No avoiding action shall be offered. The pilot is wholly responsible for maintaining separation from other aircraft whether or not the controller has passed.

traffic information. Under a Traffic Service the following conditions apply:

      • The service may be requested under any flight rules or meteorological conditions.
      • The controller shall only update details of conflicting traffic, after the initial warning, at the pilot�s request or if the controller considers that the conflicting traffic continues to constitute a definite hazard.
      • The controller may provide radar vectors for the purpose of tactical planning or at the request of the pilot. However, vectors shall not be provided to maintain separation from other aircraft, which remains the responsibility of the pilot. There is no requirement for a pilot to accept vectors.
      • The controller will be advised before a pilot changes level, level band or route.
      • Should a pilot request avoiding action, this shall be treated as a request for a change of radar service.

Classification of Airspace

The classification of airspace determines which flight rules apply and the minimum services that are to be provided in that airspace. There are 7 types of airspace in the [ICAO]; A to G, A being the most restrictive and G being the least restrictive.

Class A


  • IFR Only.
  • ATC Clearance before entry.
  • Comply with ATC Instructions.
  • All aircraft are separated from each other.

VFR flights are not permitted in Class A airspace - Special VFR is permitted in Class A Control Zones.
Class A airspace in the [ICAO] can be found in the London and Channel Island Control Zones and airways above FL245.


Class B


  • IFR and VFR.
  • ATC Clearance before entry.
  • Comply with ATC Instructions.
  • All aircraft are separated from each other.

There is currently no Class B airspace located within the [ICAO].


Class C


  • IFR and VFR.
  • ATC Clearance before entry.
  • Comply with ATC Instructions.
  • IFR flights separated from other IFR and VFR flights.
  • VFR flights separated from IFR flights.
  • Traffic Information on VFR flights passed to VFR flights, with avoidance advice if requested.

Class C airspace in the [ICAO] can be found between FL195 and FL245 throughtout the [ICAO]


Class D


  • IFR and VFR.
  • ATC Clearance before entry.
  • Comply with ATC Instructions.
  • IFR flights separated from other IFR flights.
  • Traffic Information on VFR flights passed to IFR flights, with avoidance advice if requested.
  • Traffic Information on VFR flights and IFR flights passed to other VFR flights.

Class D airspace in the [ICAO] can be found in most control zones around airports.


Class E


  • a) IFR and VFR.
  • IFR flights obtain clearance before entry.
  • IFR flights comply with ATC Instructions.
  • IFR flights separated from other IFR flights.
  • Traffic Information on VFR flights passed to IFR flights, as far as practicable.
  • VFR Flights in contact to be given traffic information as far as practicable.

VFR flights do not have to be in contact, or require an ATC clearance in Class E airspace. Class E airspace in the [ICAO] can be found in the Newcastle control zone, and the Scottish TMA.


Class F


  • a) IFR and VFR.
  • Participating IFR flights comply with ATC instructions.
  • Participating IFR flights separated from each other.

Class F airspace can be found on Advisory Routes in Scotland and Northern England.


Class G


  • IFR and VFR

Class G airspace is Uncontrolled Airspace - More than half of the [ICAO] airspace is class G, and can be found all around the country.


RVSM airspace was introduced throughout Europe in January 2002. It has also been implemented in North America, South America, Australia, Middle East, Africa, Parts of Asia and the Atlantic and Pacific Oceans.

RVSM means Reduced Vertical Separation Minima - or in plain english the reduction of the vertical separation required between FL290 and FL410 from 2000ft to 1000ft. By doing this you double the amount of airspace available, therefore doubling the traffic capacity. With the skies getting busier and busier every day the need for more room has become more and more important.

In the real world aircraft must have the following equipment aboard to be RVSM certified and therefore take advantage of the reduced separation minimum:

  • Two primary altitude reporting systems.
  • One automatic altitude-keeping device.
  • One altitude-alerting device.
  • In addition, while changing altitudes, the altitude holding device must not overshoot an assigned level by more than 150 feet.

Aircraft who do not meet the standards are excluded from RVSM airspace except for the purpose of climbing or descending to/from the CVSM airspace above FL410. (Exceptions do exist though, see bottom of page for complete listing.)

In the real world this was a costly affair for operators who still had older aircraft in their fleet. On IVAO there isnt much to it, as any aircraft can be considered RVSM, or non-RVSM. There are however a few important procedures for pilots and ATC to follow. They are detailed below.


Pilots flying through RVSM airspace continue using the Odd-East / West-Even rule up to FL410, after which the airspace becomes CVSM.

Pilot Guidelines

All pilots operating within RVSM airspace are to comply with the following guidelines:

  • Pilots flying RVSM certified aircraft are expected to file altitudes appropriate for the direction of flight in compliance with the previous table.
  • The equipment suffix W shall be filed in the flight plan to indicate RVSM certification.
  • Autopilot must be used to maintain altitude in level cruise flight. Manual trimming of the aircraft is not acceptable. If the autopilot does not work or the altitude hold mode is known to be inaccurate, the aircraft will be considered non-RVSM, and therefore not allowed into RVSM airspace. The equipment suffix "W" is not to be used on such aircraft.
  • If a pilot notices his aircraft is unable to accurately maintain altitudes with the autopilot altitude hold he/she is to consider the aircraft as not up to RVSM standards and notify ATC at once. This applies regardless of whether the aircraft is already in, or cleared to enter RVSM airspace. ATC may instruct pilots of such aircraft to leave RVSM airspace if traffic requires.
  • Pilots are to report any encounters with turbulence greater than moderate. By its nature, severe turbulence means that control of the aircraft is affected, and RVSM procedures can no longer be maintained.



ATC Guidelines

All controllers operating positions involving RVSM airspace are to follow the following guidelines:

  • All aircraft having filed /W equipment suffix will be considered RVSM certified and equipped, unless there it is apparent that the aircraft is unable to hold altitude with reasonable accuracy.
  • Aircraft not having filed /W equipment suffix, will not be cleared to enter RVSM airspace except for those aircraft meeting the conditions described in the exceptions listed below.
  • Aircraft operating in RVSM Airspace who indicate an inability to maintain altitude correctly shall be considered non-RVSM compliant. Separation for such aircraft shall be immediately increased to 2,000 feet vertically, and the aircraft shall be cleared to climb or descend out of the RVSM airspace as soon as practicable. Aircraft who are unable to make destination due to fuel requirements at lower levels will not be required to descend below RVSM airspace, but 2000ft separation will have to be maintained at all times. The idea is to remain within the rules of RVSM while not creating a fuel shortage for the aircraft involved. It is essential to pass this information to adjacent sectors/units.
  • Use of altitudes inappropriate to direction of flight (wrong-way) in RVSM airspace remain the same as outside of RVSM airspace. Aircraft cruising at such altitudes should be cleared back to correct altitudes as soon as practicable.
  • If an aircraft reports greater than moderate turbulence, use of 2,000 feet vertical separation will be required. Immediate action must be taken to provide another form of separation, including changing of altitudes, use of speed control, or re-routing.




There are a few exceptions which may allow a non-RVSM certified aircraft to operate with RVSM exclusionary airspace. For those who do get clearance into it, the following rules apply:

  • RVSM certified aircraft will receive priority for altitude assignment over non-RVSM aircraft.
  • Vertical separation of 2,000 feet will be maintained between non-RVSM aircraft and all other aircraft.
  • Aircraft wishing to climb or descend through RVSM airspace are to be granted clearance provided they do not level off within RVSM airspace, should maintain a normal rate of climb or descent (no cruise climbs/descents allowed).
  • Aircraft used by military, police and customs services are exempt from RVSM certification requirements, do not require advance approval, and will be provided with 2,000 feet separation from all other aircraft in RVSM airspace.