How do I follow ATC vectors and altitudes under IFR?

Under IFR, read back every assigned heading and altitude, set the heading bug and altitude selector, then make the commanded turn, climb or descent promptly. Use heading mode for radar vectors, verify the active autopilot modes, level at the cleared altitude and continue until ATC issues a replacement clearance.

In Aviation & Real-World Flying, the key distinction is that a vector assigns a heading, not a waypoint or ground track. ATC may amend that heading and altitude several times as traffic, weather and the approach sequence change.

What does an ATC vector tell you to do?

An ATC vector tells you to turn to and maintain a specified heading, normally magnetic unless the local procedure explicitly uses true headings. For “turn right heading 240”, turn right until the heading indicator reads 240°, then maintain it until another clearance arrives.

Do not compensate for wind by steering the GPS ground track towards 240°. Hold the assigned aircraft heading; the controller watches your radar track and supplies another vector if necessary. Likewise, do not return to the magenta flight-plan line merely because the vector takes you away from it.

A vector is different from “direct FIX”, “intercept the localiser” or “resume own navigation”. Those instructions transfer you from heading guidance to a defined route or course. Our explanation of how radar vectors sequence aircraft during departures and approaches covers that wider controller workflow.

How should I action a heading and altitude instruction?

Use a listen, read back, set, execute and monitor flow for every combined ATC instruction.

1. Capture the complete clearance. Write short notes such as R240 / 4000 for “turn right heading 240, descend and maintain 4,000”. If workload prevents a safe response, maintain control and tell ATC to stand by.
2. Read back the safety-critical parts. Include the turn direction, heading, altitude and callsign: “Right heading 240, descend and maintain 4,000, Callsign.” A correct readback gives ATC an opportunity to catch a wrong number.
3. Set and cross-check the controls. Move the heading bug to 240 and the altitude selector to 4,000. Confirm both values on the primary flight display or instruments before engaging an autopilot mode.
4. Execute promptly. Start the commanded turn and climb or descent without unnecessary delay. If you cannot comply because of performance, weather, terrain or another safety issue, say “unable” and request an alternative.
5. Verify the result. Check the flight mode annunciator, turn direction, altitude trend and airspeed. Reduce the vertical rate early enough to prevent an altitude overshoot, then confirm that altitude hold captures at the cleared level.

A mistake we see constantly in simulators is setting the correct altitude in the selector but never activating a climb or descent mode. The selected number is usually only a limit or capture target; it does not by itself make the aircraft move vertically.

Which autopilot modes follow ATC instructions?

Use heading select for a radar vector and a suitable vertical mode for the assigned altitude, but treat the flight mode annunciator as the final authority. Mode names and capture logic vary between aircraft.

VS holds a vertical rate and can drive the airspeed dangerously low in a climb or high in a descent if left unattended. FLC or an indicated-airspeed mode pitches for the selected speed, but still requires appropriate power and monitoring.

If the autopilot chooses the wrong turn direction after a large heading-bug change, disconnect or guide the bug progressively in the instructed direction as appropriate for that aircraft. When hand-flying, use the bug and selected altitude as references; our guide to interpreting flight-director pitch and roll commands explains how those cues relate to the active modes.

Altitude wording that changes the clearance

The exact phrase determines when you may move and where you must level, so an expected altitude or a flight-plan altitude is never a substitute for an ATC clearance.

• “Climb/descend and maintain 6,000” means begin promptly and level at 6,000 unless ATC adds timing or procedural restrictions.
• “At pilot’s discretion” gives the pilot control over when to start within the applicable rules. Procedures for intermediate level-offs and returning to a vacated altitude vary by jurisdiction.
• “Expedite climb/descent” requests the best practical rate without compromising aircraft limitations or safety. Report immediately if unable.
• “Cross FIX at or above/below 5,000” imposes a restriction at that fix; it does not necessarily require level flight at exactly 5,000.
• “Climb via” or “descend via” normally invokes the published procedure and its restrictions, subject to the exact clearance and local rules.

Below the transition altitude, fly the assigned altitude using the correct local pressure setting. At a flight level, use standard pressure. Transition procedures differ by country, so changing the selector at the wrong point can produce a significant altitude error.

On an approach, an instruction such as “maintain 3,000 until established, cleared ILS” means hold 3,000 until established on the authorised approach course, then follow the published vertical profile. Do not descend merely because a glideslope indication appears; check the charted instrument-approach altitude and intercept requirements.

When can I leave an assigned heading or altitude?

Leave an assigned heading or altitude only when ATC replaces it, an authorised procedure takes effect, or immediate safety requires a deviation.

• Remain on a vector until given another heading, cleared direct, told to resume own navigation or authorised to intercept and follow a course.
• Remain at the cleared altitude until ATC assigns another one or the clearance permits descent or climb through a published procedure.
• A frequency change or controller hand-off does not cancel the previous heading or altitude.
• An altitude mentioned as “expect” is planning information, not permission to climb or descend.
• If an approach clearance or altitude restriction is ambiguous, maintain the last unambiguous clearance and ask ATC to confirm.

Unclear, impossible or unsafe instructions

Tell ATC immediately if a clearance is unclear or cannot be flown safely; do not silently substitute your own heading or altitude. Use plain language such as “unable”, “say again heading”, or “confirm descend to 2,000”. In real operations, the pilot in command retains responsibility for terrain, weather, aircraft limitations and collision avoidance.

Built-in simulator ATC can issue late descents, poor intercepts or terrain-threatening altitudes. Preserve aircraft safety, compare the instruction with the chart and use our guidance on rejecting or correcting unsafe simulator ATC clearances rather than following a bad command blindly. If communications fail in real flight, apply the published lost-communications procedure for the jurisdiction and clearance involved.