The Difference Between ATC Clearances and Advisories

The following transmission from a tower controller has a clearance and an advisory. Can you tell which is which?

ATC says, “Skyhawk 9130 Delta, Runway 16, line up and wait. Traffic will be crossing downfield.”

When the controller said, “Runway 16, line up and wait,” he was directing Skyhawk 9130 Delta to do something. When he said, “Traffic will be crossing downfield,” he was advising the pilot of a circumstance that is relevant to the flight.

When a controller tells you to do something, you are required to read back that information. The readback lets the controller evaluate your understanding of what he just told you to do. If after listening to your readback he feels you did not understand him correctly, he can provide additional information to clarify his meaning.

An advisory message from ATC is designed to make you aware of a circumstance that affects your flight. ATC advisories do not require you to take action. Note in our example, “Traffic crossing downfield” tells you why ATC is directing you to line up and wait. It’s good information but does not require you to do anything directly in response. Lining up and waiting on the runway happens in response to the clearance that came earlier, not in response to the advisory that came after the clearance.

In summary, when ATC tells you to do something, read back what he tells you to. When ATC provides information that does not require you to do anything, there is no requirement to read back the information.

Here’s how you would reply to the example transmission at the beginning of this article. “Skyhawk 9130 Delta, Runway 16, line up and wait.” That’s it. You would note, but not read back the bit about traffic crossing downfield.

One last bit of advice. If ATC gives you advisory information only, acknowledge the advisory with your call sign. For example, if ATC says, “Skyhawk 9130 Delta, traffic your 1 o’clock and 10 miles, westbound, 1,000 above you, no factor.” This advisory is helpful but it does not require you to do something with your aircraft in response. Simply reply, “Skyhawk 9130 Delta.” This tells the controller you heard him. Saying nothing in response to an advisory-only would leave the controller wondering whether you heard him. Absent any acknowledgement from you, he would likely repeat the advisory.

Questions about the distinction between a clearance and an advisory? Comment below or write to me directly at

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