I've read somewhere that "a clearance is not valid until read back correctly," but I can't remember where or find a specific rule saying that.

I understand some clearances can be accepted with "Wilco" or similar in lieu of a full readback, but assume this isn't one of those cases.

For example, is it technically a violation to cross the runway hold bars before you finish reading back a takeoff or crossing clearance?

  • 1
    $\begingroup$ I know a guy who was busted for blowing through an altitude in a clearance, even though he'd been cleared higher before reaching it, because he blew through the original altitude before he'd read the clearance back. $\endgroup$
    – John K
    Nov 9, 2019 at 21:15
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    $\begingroup$ @JohnK What FAR did they say he violated? $\endgroup$
    – StephenS
    Nov 9, 2019 at 22:54
  • $\begingroup$ It was in Canada so it would be a CAR (similar). Not sure exactly. It's one of those things were 99.9% of the time the controller would let it slide, but if the controller was pissed off at you for something it was something they could do. $\endgroup$
    – John K
    Nov 10, 2019 at 0:24
  • $\begingroup$ I would like to see the controller defend that on appeal. A total dick move. $\endgroup$ Nov 10, 2019 at 2:32
  • $\begingroup$ Imagine a scenario where you THINK you have been instructed to cross a runway, but the controller actually said something else. While reading back, you proceed to taxi across the runway. The controller doesn't have a chance to stop you, since he can't talk on the radio as long as you are talking. $\endgroup$ Nov 13, 2019 at 12:46

2 Answers 2


Interesting question - although not FAA, I hoped the UK's CAP 413 would hold some insight as it tends to follow ICAO rules:


Page 25 is the relevant chapter, and while it doesn't outright say the clearance is not valid it is very strong in its readback requirements. The following language applies to runway entry/take off/landing:

The stringency of the read back requirement is directly related to the possible seriousness of a misunderstanding in the transmission and receipt of ATC clearance and instructions. ATC route clearances shall always be read back unless otherwise authorised by the appropriate ATS authority

The ATS messages listed below are to be read back in full by the pilot/ driver. If a readback is not received the pilot/driver will be asked to do so. Similarly, the pilot/ driver is expected to request that instructions are repeated or clarified if any are not fully understood.

[Lists the relevant activies, including runway entry]

It also points to ICAO Doc 4444:


With similarly direct wording:

The flight crew shall read back to the air traffic controller safety-related parts of ATC clearances and instructions which are transmitted by voice. The following items shall always be read back:

a) ATC route clearances;

b) clearances and instructions to enter, land on, take off from, hold short of, cross, taxi and backtrack on any runway; and

c) runway-in-use, altimeter settings, SSR codes, level instructions, heading and speed instructions and, whether issued by the controller or contained in automatic terminal information service (ATIS) broadcasts, transition levels.

It seems clear to me that ICAO, EASA and CAA standpoint is that readbacks are completely mandatory, and the clearance has not been fully delivered until the readback is completed. The readback is a controller final opportunity to correct a potentially critical misunderstanding or communication and it seems to me that proceeding without reading back, and waiting for any call of "Negative" is negligent.

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    $\begingroup$ That is clear a readback is required, but it doesn't seem to address whether the clearance is valid before that is complete. $\endgroup$
    – StephenS
    Nov 9, 2019 at 22:56

Another question touched this particular topic so I am linking it for your benefit.

When has a pilot legally accepted an ATC clearance or instruction?

The consensus is that the pilot is the PIC (Person In Command) and has the final authority. So there is actually no formal or explicit answer to your question.


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