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I'm sure many people have heard about the communication between a Delta flight 2244 and Atlanta tower being on news today.

When the Controller informs the Pilot he is on a wrong taxi-way, things get a little heated up.

Regardless of who was right who was wrong, there were many lives involved (i'm sure they were not put in danger) but then who takes precedence in such a situation?

Can the controller tell the aircraft to stop dead in its tracks or turn back to the hanger for violating his instructions because there are other planes coming in to land and this can become a little dangerous?

Note: I am fully aware that no one was close to danger and lives were not at risk, but still pilot did worry that there is another plane coming down.

Was the pilot right in saying

We'll taxi out there any way we want when you tell us to.

For those who missed. Here is the whole story

Note

Please note that this reporting on that article is misleading. It is about taxi clearance and not landing on a wrong runway, However I have no control of what reporters write in their articles. The transcript itself is clear.

Hear the original ATC audio here

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3 Answers 3

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It isn't a black and white issue of who has higher authority. A pilot in command (PIC) is the ultimate authority for the safe operation of his airplane. An air traffic controller is the authority for the block of airspace or pavement he controls.

When you are operating under ATC, it is your responsibility to comply with their instructions as long as they fall within the regulations, they are safe and you are able to comply, If ATC issues an instruction contrary to regulation or something that would compromise safety, that is when you exercise your PIC authority to deviate from their instruction. If you are unable to comply, you exercise your authority to deviate and explain why you are deviating. When you cannot comply with an ATC instruction, for whatever reason, it is the job of ATC to accommodate your and move other airplanes out of your way.

The regulatory basis for the PIC authority and ability to deviate from ATC instructions is in 14 CFR 91.3

§91.3 Responsibility and authority of the pilot in command.

(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.

(b) In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

(c) Each pilot in command who deviates from a rule under paragraph (b) of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator.

The basis for ATC's authority is 14 CFR 91.123

§91.123 Compliance with ATC clearances and instructions.

(a) 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. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.

(b) Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.

(c) Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible.

(d) Each pilot in command who (though not deviating from a rule of this subpart) is given priority by ATC in an emergency, shall submit a detailed report of that emergency within 48 hours to the manager of that ATC facility, if requested by ATC.

(e) Unless otherwise authorized by ATC, no person operating an aircraft may operate that aircraft according to any clearance or instruction that has been issued to the pilot of another aircraft for radar air traffic control purposes.

Absent an emergency, an urgent need* or an inability to comply with ATC, a pilot is required to obey an ATC clearance. Given this relationship and its exceptions, its is hard to quantify who has a "higher" authority. Both are the ultimate authorities of their domains, but who overrules who is dependent on the situation. In general however, ATC will be issuing proper clearances that a pilot is bound by regulation to follow, though the pilot must exercise his authority to execute that instruction in a safe manner.

*Urgent needs include things like TCAS RA events and things like weather deviations. In most cases ATC will help you out with a deviation, but if a controller refuses to allow a deviation, I would happily exercise my PIC authority to safely operate my airplane and turn left/right a few degrees rather than penetrate a thunderstorm updraft.


In the particular case above, the audio exchange between DL2422 and Atlanta ground is

DL2422: Good morning Atlanta ground, delta 2422 approaching 3 South taxi Quebec

DL2422 is at the southern exit of ramp 3 and requesting taxi with ATIS information Q.

Ground: Delta 2422, behind the MD88 from your right, runway 27R, taxi via Mike and hold short of Dixie.

ATC has instructed DL2422 to let an MD88 pass from right to left, to taxi on taxiway M to runway 27R but to hold short for taxiway D (in ATL D is "Dixie" due to the larger number of "Delta" airplanes). To follow this instruction, an airplane should taxi south from spot 3S on taxiway L5, cross L and then turn left on M, then taxi on M, stopping short of D and awaiting further instruction.

DL2422: OK behind the 88 from the right, 27R Mike short of Dixie, DL2422

Here, DL2422 acknowledges this correctly.

Ground: DL2422 they won't let you go to Charlotte until 57 minutes after the hour, time now 29 after

DL2422: OK copy 57, DL2422

DL2422 has been issued a wheels-up time, but their taxi clearance has not been amended. They are still cleared to taxi via M short of D. Sequencing to meet this time will happen east of D in further clearances.

Ground: DL2422, you are supposed to be on M

DL2422: Yes sir, we're going out there right now.

Ground: Looks like you joined L

DL2422: You know what, we'll taxi out there any way we want unless you tell us to, I don't like your attitude.

Ground: I don't have an attitude sir, I'm just saying it looks like you joined L instead of M and I'm just trying to correct you before you stay on L.

DL2422: Ok, cause my god, there's another plane out there, its like 6 miles away. Your attitude is really something sir, we're out here on M. Good morning.

Ground: Good morning. There was no attitude, I was just trying to correct you, that's my job to correct you if you mess up. I'm just trying to make sure everyone is doing what I ask them for certain reasons.

DL2422: You make a mistake every 2-3 minutes, but my attitude is not like yours, we're out on M and you didn't tell us how to get there so next time you can try doing that.

The DL captain is making a scene and a very roundabout argument that the taxi route did not specify how he was supposed to transition from spot 3S to taxiway M. I agree that this is the case, but do not understand why any assumption would be made other than to taxi straight out and turn left on M.

This is a good example of a minor deviation that had DL2422 just turned right and then left and said "oops, fixing that, joining M, thanks!", then that would have been the end of it. This captain's unprofessional display will instead net him disciplinary action and classify his deviation as "willful" rather than "accidental".

For a clearer visualization of the event, see this image:
ATL
In this image, the green circle is the starting point of DL2422 and the blue line is the cleared taxi route with the assumed transition to M via L5. The short red line is the initial taxi route DL2422 took. It is not clear where they transitioned to M, so I did not extend the red route past the first possible transition.


There appears to be some controversy over the verbiage of "behind" used in the ATC taxi clearance. The only reference I can find to this word in a cursory search is in FAA order 7110.65 (ATC procedures) in section 3-7-2 that gives example taxi clearances. This does not define "behind" but does give distinct examples that clearly differentiate "behind" from "follow". Given that I cannot find a better reference, all I can offer instead is years of experience in a 121 cockpit based at busy airports like IAH and EWR and plenty of visits to others like ORD, ATL, LAX, DTW, IAD, etc where clearances involving the words "behind" and "follow" are quite common.

  • Behind Use of this word means that you are waiting for an aircraft to pass. You are giving right of way or yielding to the traffic in question. This clearance is often given when holding short of an intersection and waiting for perpendicular traffic to cross the intersection before you continue through it. Much like waiting at a stop sign in a car. You are not expected to follow the airplane in question and even if you are assigned a turn to taxi along the same route as the airplane, you have your own clearance and are not following that aircraft.

    Examples:

    • "Continental 1234 taxi to runway 22R at W via K hold short of S", followed by "Continental 1234 you'll see a B767 passing right to left on S, behind him continue to runway 22R at W via K R hold short of W"

    In this case it is quite explicit that an airplane will be passing across your route of taxi and after it passes you are to continue taxiing straight ahead -- not to follow that airplane. Consider an alternate setup:

    • "Continental 1234 taxi to runway 22R at W via K hold short of S", followed by "Continental 1234 you'll see a Citation from the right at S, behind him taxi via S W hold short of R.

    In this case, you are waiting for traffic from the right again, but this time you are turning left after it passes. You will be taxiing behind it, but you are not following it. The Citation has a clearance to taxi S, cross runway 29, to parking. Your clearance is S turn right on W -- to follow the Citation would be wrong.

  • Follow Use of this word means you are going to fall in behind this airplane and follow it wherever it goes. You clearance is no longer a specific taxi route, but simply to follow the airplane.

    Examples:

    • "Jetlink 1234, your sequence is the third airbus to your right, the one painted purple. Follow that airplane to runway 22R at W. Once behind him, monitor tower, you are number 28 for departure.", which will be followed by
    • "United 3412, hold short of J, let the EMB-145 get in line then follow him to runway 22R at W. Monitor tower passing L, you are number 29 for departure"

    These clearances are used to get airplanes in line in a specific sequence and simplify giving repeated complex taxi instructions when you can just follow to conga line to the runway.

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What does the phrase "behind the MD88 from the right" mean? If it means after the MD88 passes you from right to left, then do what you want to get to where we told you. Or if it means (follow) behind the MD88, passing you from right to left. Perhaps ATC was not AS clear as they could have, or maybe, should have been. Please note, I completely agree that the Captain should have just 'manned up' and agreed that he incorrectly entered L, and asked ATC for correction guidance. –  CGCampbell Jul 28 at 18:25
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@CGCampbell it means "Pass behind the MD88 (airplane) approaching from your right". In other words, wait for him to go by before you start taxiing. –  casey Jul 28 at 18:29
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"When you cannot comply with an ATC instruction, for whatever reason, it is the job of ATC to accommodate your and move other airplanes out of your way." Or they might just move you out of the way, instead, as the case may be (except, of course, in the case of an emergency.) If, for instance, a plane were unable to hold the assigned speed for an approach, they might be sent around rather than sending another plane around. The controller will accommodate your inability to follow the initial instruction, but it might be you that goes around rather than someone else, except in an emergency. –  reirab Jul 28 at 21:14
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The professional way for ground to handle it would have been to give taxi instructions from the current position when the discrepancy was noticed. Assuming intermediate taxi instruction was given earlier the pilot knows he took a wrong turn; ground knows he took a wrong turn; ground knows that the pilot knows he took a wrong turn. What ATC said was a dig - that's how I would have taken it. ATC started it and there's no time for that crap in the middle of "the push" at Atlanta of all places. OMG. How the pilot responded was an embarrassment to every flight crew on frequency. –  radarbob Jul 29 at 1:14
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@Articuno I have added some text to the answer addressing "behind" vs "follow". Its hard to dig up a citation for this, but these are commonly used at busy airports and anyone operating there should be familiar. –  casey Jul 29 at 1:55

Pilots need to follow instructions and clearances of air traffic control, unless this would pose a threat to aircraft security or is simply not feasible.

The ATC has the possibility to instruct an aircraft on ground to stop immediately or at the next intersection, etc.

"DAL123, hold position"
"DAL123, hold short of Alpha"

If the pilot is unable to comply for whatever reason, he must make the air traffic controller aware of this:

"DAL123, unable"

ATC has no way of forcing someone to return to the gate, if the pilot does not follow the instructions to return. They could even take off without clearance, but rest assured that they would be met upon arrival at their destination and an investigation opened into why they did not follow instructions. This is also true for using a wrong taxiway, the pilot will be asked to stop and rerouted via the correct taxiways. Mistakes happen, but when instructed to follow a certain set of taxiways, pilots must comply unless unable.

There is one thing however that needs to be mentioned: "The pilot in command is ultimately responsible for the flight and its safety". So if the pilot decided it's better for him to use a certain taxiway due to weight/wingspan or he cannot land on a certain runway, he can make ATC aware and they will try to accommodate.

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It was my experience that the most direct route was understood between the controller and pilot. Consider the ramifications if this were not the case. If another route is needed, it is up to the PIC to inform the controller of that need. Also, if there is ANY question on either side about the instructions or requests, key up the mike and ask! Safe, Orderly, and Expeditious flow of air traffic.

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