Non-Towered Airport Operations: A Flight School Guide to AC 90-66C and the Traffic Pattern

A line of three trainers stacks up on the 45 for runway 27 at the local non-towered field on a Saturday morning. Two students are calling in altitude and intentions; one is silent because the radio cord is unplugged. A fourth airplane announces a five-mile straight-in to the same runway and continues without yielding. Nothing collides, but the chief instructor watching from the ramp knows the day's near-miss already happened, and the only question is which student goes home with the wrong picture of how this is supposed to work.

The vast majority of public-use airports in the United States operate without a control tower or with a tower that closes at night. For most flight schools, the airport the lessons fly out of is one of them, and the rules of that field are not a regulation a student reads once and forgets. They are the operating manual a school teaches every day. The reference for those rules is AC 90-66C and the regulations it sits on top of.

What AC 90-66C Is, and What It Is Not

AC 90-66C, issued in June 2023, is the FAA's current advisory on operating at airports without an operating control tower. It is guidance, not regulation. The legal weight at the field comes from 14 CFR 91.126 for Class G airspace and 91.127 for Class E, which together set the rule that turns at non-towered fields are to the left unless approved markings or lighting say otherwise. AC 90-66C fills in everything 91.126 leaves to recommended practice: pattern altitude, entry technique, what to say on the radio, who has the right of way when patterns overlap.

The reason the AC matters is that recommended practice is what an inspector, an insurance underwriter, and an NTSB report after an incident will all measure a pilot against. A school whose SOPs match AC 90-66C is teaching the version of non-towered operations the rest of the system already assumes.

Traffic Pattern: Altitude, Direction, Entry

The default pattern at a non-towered field is to the left, at 1,000 feet AGL for piston aircraft and 1,500 feet AGL for turbines and large aircraft, unless the airport's chart supplement or segmented circle says otherwise. The published TPA is a value, not a suggestion, and a school whose airplanes routinely fly 200 feet high on downwind is one whose students will be the high-and-tight traffic at the next field they visit.

AC 90-66C recommends the 45-degree entry to the downwind at pattern altitude, and recommends against modified entries such as crosswind-to-downwind unless the geography of the airport forces it. Where the AC quietly tightened the language from the older revision is on straight-in approaches. They are not prohibited at non-towered fields, and IFR traffic is often expected to fly them, but a pilot on a straight-in does not have priority over an aircraft established in the pattern and must give way. A student being taught that calling a straight-in is a substitute for pattern integration is being taught the version of non-towered ops that ends up in the accident summaries.

Self-Announce: What the AC Now Asks You to Say

The communications change in 90-66C that affects training the most is in the self-announce itself. The AC asks pilots to include the airport name at the start and end of every CTAF transmission, identify the aircraft by type rather than only by tail number, and use the specific runway number rather than "active." "Skyhawk three-four-foxtrot, ten miles northeast, inbound to land, runway two seven, Sky Harbor" tells the next pilot something. "Traffic in the area, three-four-foxtrot, planning the active" tells them almost nothing.

The reason for the change is that a CTAF is often shared by several airports within radio range. Without the airport name on both ends, a transmission about a base turn at one field gets heard as a base turn at another, and pilots build a mental picture of traffic that is not where they think it is. This is one of the patterns that shows up in improving flight school operations: the standardization is not about elegant phraseology, it is about the next pilot in the pattern being able to act on what they heard.

Where Non-Towered Procedures Show Up in the Syllabus

Pattern competence is the through-line of primary training, not a single lesson. It starts on the first lesson when the instructor demonstrates the 45 entry and the downwind call, and it does not finish until the student is signed off for the solo and proves they can run a pattern without prompting. Schools that treat AC 90-66C as a Stage One reference and never come back to it produce students who can fly the local pattern fluently and freeze the first time they fly into a field where someone announces a base entry from the east.

A pre-solo phase check should include a no-radio scenario and a busy-pattern scenario, because both happen. A radio call missed for a stuck mic is a pilot who has to read the pattern with the eyes alone, and a pilot who can do that at the home field is the only kind a chief instructor should sign off to fly there alone.

A Standard SOP a School Can Adopt

The schools that hand new instructors a one-page non-towered SOP are the ones whose students all sound alike on the radio. The SOP does not need to invent anything. It needs to state the home airport's pattern direction and TPA, the standard 45 entry, the self-announce points (ten miles out, entering the 45, downwind, base, final, and clear of the runway), the phraseology with airport name on both ends, and the school's policy on straight-ins for instrument training. The same SOP should say what an instructor does when a transient pilot is flying the pattern non-standard: announce position clearly, yield, debrief afterward.

An SOP that lives in a binder nobody opens is not an SOP. An SOP that is part of instructor onboarding and shows up in every stage check is the one that survives the day the chief instructor is not there. This is the same operational discipline that makes instructor scheduling actually hold together: the standard exists in writing, and the people doing the work were taught it the same way.

The Field Is the First Thing the Student Learns to Read

A flight school's reputation at a non-towered field is set by the students it sends into the pattern. The ones who call clearly, fly the published altitude, enter on the 45, and yield to traffic on final are the school's advertisement to every other pilot on frequency. The ones who fly the pattern they think looks safe, on a frequency they share without naming, are the reason a fast-moving transient ends up cutting them off and the local airport manager ends up with a phone call. AC 90-66C is not exotic guidance. It is the version of normal that flight schools are uniquely positioned to make universal at their home fields.