I think we’re in agreement. :) I was referring to § 91.123 (a), which reads in part (emphasis added): “When an ATC clearance has been obtained, no pilot in com

I think we’re in agreement. :) I was referring to § 91.123 (a), which reads in part (emphasis added): “When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.” I.e. when ATC tells you “turn left heading 135,” unless you have a very good reason not to, you must turn left to heading 135. The part I didn’t emphasize is of course exactly what you’re saying. I suppose another way to phrase what I meant is that while ATC is the boss “in the small,” the PIC is the boss “in the large,” and I don’t think non-pilots think of it that way.