What's the maximum altitude ATC would deal with?

Any example of jets service ceiling certified for above 45.000? Commercial & Business jets?

  • 2
    $\begingroup$ The max altitude ATC would deal with is the transition altitude. Above that it's flight levels. $\endgroup$ Apr 7, 2018 at 14:42

3 Answers 3


There are many examples of aircraft with high service ceilings. While most commercial aircraft have service ceilings of FL410 and rarely fly even that high, many business jets have a service ceiling of FL510, such as the Dassault Falcon 7X, Gulfstream G650, and Bombardier Global Express.

That being said, military jets can fly higher and will be talking to ATC while in their airspace. Fighter jets are capable of high altitude flight, and planes like the U-2 and Global Hawk still fly up there as well.

In the US, all aircraft from FL180 to FL600 must be in contact with ATC, but above this they are not required to. ATC will still provide services when able though.

  • 5
    $\begingroup$ Your link to the U-2 wiki was apparently lost when they ascended past FL600... $\endgroup$ Apr 6, 2018 at 23:08
  • 1
    $\begingroup$ @TemporalWolf haha, thanks for letting me know! $\endgroup$
    – fooot
    Apr 7, 2018 at 1:19
  • $\begingroup$ If above FL600 they are not required to be in contact with ATC, other than TCAS, what prevents collisions? $\endgroup$ Apr 8, 2018 at 9:28
  • $\begingroup$ @user1997744 I am no expert and have no clue how cockpit looks like (demonstrating my knowledge about planes); but I think planes that fly that high have on board radar - preventing collisions. $\endgroup$
    – Kyslik
    Apr 8, 2018 at 15:51
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    $\begingroup$ @user1997744 the fact that there are so few airplanes that ever fly that high, and they will probably prefer to stay in contact with ATC for safety. $\endgroup$
    – fooot
    Apr 8, 2018 at 17:30

There is no maximum altitude for ATC service. ATC will deal with anything that flies over their airspace.

In the US, Class A airspace ends at FL600. Meaning if you fly above 60,000 feet (pressure altitude), you are not required to contact ATC, because it is Class E airspace. But that does not mean ATC will deny talking to aircraft at that altitude.

Practically speaking, very few aircraft (if any) can get above FL600. Chances are if you can get there, you are in an experimental military aircraft or spaceship.

Flights above FL400 are common for private and business jets. They are managed by ATC.


The other answer are correct that above FL600 you no longer need to be in contact however its worth noting there is some interesting historical implications to this.

The only civilian aircraft that routinely operated above the majority of other aircraft was the Concorde, which during its time cruised up around FL500. In his interview on Omega Tau one of Concorde pilots discusses this very situation. Essentially above ~FL450 they were allowed to transition altitudes as they saw fit and without contacting ATC essentially since they knew no one else was up there. He mainly discusses it in the context of fuel burn and how as the aircraft burned fuel it had a tendency to slowly drift up. ATC allowed them to do this (and not stick to an assigned altitude) as they could not really drift up into anyone.

  • $\begingroup$ wow thanks that helps me honestly :) didn't know they could change altitude without contacting ATC. $\endgroup$ Apr 6, 2018 at 21:45
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    $\begingroup$ They could be in contact with ATC, but simply given a block altitude clearance, FL 500 block 600 or something. While their autopilot certainly could maintain a precise altitude, it's more efficient to perform the slow climb as fuel burns off, so that's what the block altitude clearance allowed them to do. You sometimes hear aircraft getting block altitude clearances, although it's not common. $\endgroup$
    – Ralph J
    Apr 7, 2018 at 2:20
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    $\begingroup$ Block altitudes are often requested when the air is turbulent and maintaining altitude becomes difficult, especially for small aircraft crossing a weather front where the winds are changing a lot as one example. $\endgroup$
    – CrossRoads
    Apr 9, 2018 at 14:37
  • $\begingroup$ @RalphJ in the podcast he does not really touch on that but makes it seem as though that was not the case and they were aloud to drift around merely because no one was up there. $\endgroup$
    – Dave
    Apr 9, 2018 at 15:08

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