70,000ft is relevant, possibly, in that the upper limit of controlled airspace is 66,000 (or Flight Level 660, I should say). Above that, you can do what you like without reference to ATC.
@rodan started
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70,000ft is relevant, possibly, in that the upper limit of controlled airspace is 66,000 (or Flight Level 660, I should say). Above that, you can do what you like without reference to ATC.