A recent interpretation by the FAA’s chief counsel answers the question whether the rule requiring compliance with ATC instructions applies to a pilot flying under visual flight rules in Class E airspace. The counsel answers yes. He cites as authority FAR 91.123(b), which reads: “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.”
Probably what engendered the question is that a pilot flying VFR in Class E airspace—although it is controlled airspace—is not required to communicate with ATC. As a reminder, Class E is all of the controlled airspace that is left over after taking out the specific classes A, B, C, and D of controlled airspace. Class E comprises the bulk of the airspace in which we operate. However, if a pilot, although not required, is communicating with ATC—for example, receiving flight following—and ATC issues an instruction, the pilot must comply with that instruction. On the other hand, if a pilot is flying in Class G (uncontrolled) airspace, ATC is not controlling that airspace and technically should not be issuing instructions. The rule does not apply.
The companion rule on clearances also is contained in FAR 91.123, in subsection (a) in a more extended form. It states: “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.”
The difference between a clearance and an instruction is ordinarily clear from the context and the wording—for example the use of the word “cleared.” But not always. It is sometimes challenging to tell the difference. The Pilot/Controller Glossary of the Aeronautical Information Manual offers some help by defining and giving examples of ATC instructions
as “directives issued by air traffic control for the purpose of requiring a pilot to take specific actions,
e.g., Turn left heading two-five-zero, Go around, Clear the runway.”
As to understanding the difference, the best advice I have been given by a controller friend, perhaps tongue in cheek, is that when it is not clear from the context or the wording of a controller’s communication, you should be able to tell the difference by the “tone” of the controller’s voice.
Busted clearances and instructions continue to result in FAA enforcement actions against pilots. So, this is a good place to repeat our advice to pilots that they should read back all clearances and instructions to the extent practical. Pilots understand that a read-back may be impractical in some instances, such as frequency congestion. My advice is based on an old NTSB precedent (NTSB is an appeals court in FAA enforcement cases) that if a pilot reads back a clearance or instruction that he or she misunderstood, and the controller does not correct the pilot’s misunderstanding, any violation of the clearance or instruction is excused. The FAA, unhappy with this precedent, blunted it by publishing a legal interpretation saying that a pilot in such a situation is in violation, even though his or her misunderstanding was not corrected by ATC. The FAA cited a provision in the Federal Aviation Act that said that the NTSB is “bound by” FAA interpretations unless they are arbitrary, capricious, or otherwise not in accordance with law.
Hold on. Since then, Congress has enacted the Pilots Bill of Rights that repealed the “bound by” FAA Act provision. The FAA continues to insist that it is entitled to the “deference” (as opposed to “bound by”) generally accorded to federal agencies under general administrative law. This raises a neat question of law that has yet to play itself out. Nevertheless, I still encourage readbacks to the extent practical for this and other important safety reasons. Indeed, currently controllers are, more and more, asking for readbacks. Readbacks are not required by regulation, but the controller’s direction for a readback is an instruction that, as I explained, is regulatorily binding as an instruction.