Name	Data Type	Definition
upperLimit	ValDistanceVerticalType	The vertical distance, measured relative to a separately specified upper limit reference, of the upper bound of an airspace layer or block. Where airspace layer is the portion of airspace between two specified vertical levels.
upperLimitReference	CodeVerticalReferenceType	The reference surface (Mean Sea Level, Ground, standard pressure, etc.) used for determining the value of the lower limit of an airspace Layer or block. Where airspace layer is the portion of airspace between two specified vertical levels.
lowerLimit	ValDistanceVerticalType	The vertical distance, measured relative to a separately specified lower limit reference, of the lower bound of an airspace layer or block. Where airspace layer is the portion of airspace between two specified vertical levels.
lowerLimitReference	CodeVerticalReferenceType	The reference surface (Mean Sea Level, Ground, standard pressure, etc.) used for determining the value of the lower limit of an airspace Layer or block. Where airspace layer is the portion of airspace between two specified vertical levels.
altitudeInterpretation	CodeAltitudeUseType	Indicates how the upper and/or lower altitude values should be interpreted.

Association	Multiplicity	Role	To	Role description
hasAnnotations	0..*	annotation	Note
isRestrictedTo	0..1	discreteLevelSeries	StandardLevelColumn	Restriction of the AirspaceLayer to a number of standard IFR or VFR levels.

From	Association	Multiplicity	Role	To	Role description
AerialRefuellingAnchor	concerns	0..*	verticalExtent	The vertical extent of the AerialRefuellingAnchor.
AerialRefuellingTrack	concerns	0..*	verticalExtent	The vertical extent of the AerialRefuellingTrack.
AirspaceActivation	concerns	0..*	levels	The level and time associated with the airspace usage part.
AirspaceLayerClass	concerns	0..*	associatedLevels	The levels and times associated with the airspace class.
RouteAvailability	concerns	0..*	levels	The level and time block referenced by the usage.

1 - Aerial Refuelling , 1 - Standard Levels , 2 - Aerial Refuelling Availability , 3 - Airspace Classification , 4 - Airspace Activation , 4 - Route Availability