Assigning a Transition Altitude

Much has been written about this, but still I get a lot of questions from trainee ATCs.
This topic is about: what transition altitude does the ATC assign to an aircraft.

Mark has written a tutorial for pilots, on when, and when not to request a Transition.
What we see in Mark’s post, is that you only request a transition, when you are passing through an airport’s airspace. Above 5000 AAL (Above Aerodome Level), don’t contact Tower!

For ATC’s to know what altitude to assign to an aircraft which is transitioning through your airspace, you need the following:

  • aerodome level of your airport
  • pattern levels of propellor aircrafts - in IF these are set to: 1000 feet Above Aerodrome Level (AAL)
  • pattern levels of airliners - in IF set to 1500 feet AAL

So this leaves room for aircrafts to transition through airspace.
The picture below assumes that the Aerodrome Level is 1000 feet ASL.

Remember: altitude assigned by an ATC is always ASL.

So for airports at sea level, transition altitide assigned to an aircraft can be between 1500 - 5000 feet.
For an airport, somewhere on the high grounds at 4500 feet, transition altitude assigned should be 6000 - 9500 feet.

Now…many pilots on IF fly their patterns a lot higher than 1000 or 1500 feet AAL.
If you as ATC have a few of these high-flyers doing patterns, I suggest you pick the top part of the transition space, to allow an aircraft to transition safely.

Note: For us in IF, it is safe to assume that AAL is the same as AGL


Another great explaination thank you 👍 Could you just confirm some of the abreviations compared to in app

AAL is the same as AGL? (Above Ground Level)


I did some searching on AAL and AGL.
What I found was that:
AAL is altitude from terrain of the airport, based on a reference point at the airport.
AGL is altitude measured from the airports ground.

Again, for IF we can assume AGL and AAL are the same.


The community can always trust you to make these excellent guides, well made thread!

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Bookmarked. This is very useful. May I ask what a Aerodrome/Airdrome is? Wikipedia’s answer didn’t make since. 😅

As far as I know, aerodrome is simply another wording for airport, though it’s usually classified such at smaller airports, mainly GA.

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For IF we can assume an aerodrome is the same as an airport.

But there are differences: Difference between Airport and Aerodrome | Airport vs Aerodrome

From what I read here:
Aerodrome: the area where flights can takeoff and land. It can even be a strip of water.
Airport: includes everything: runways, airport buildings, etc.


I know this is an older topic, but this was very helpful as a trainee ATC. Thanks for the tutorial!

Can now be found in the ATC Manual here. Thanks for your contribution!