What are SIDs, STARs and instrument approach procedures?

SIDs, STARs and instrument approach procedures are published IFR procedures for different phases of flight. A SID leads an aircraft from departure into the en-route structure; a STAR brings it into the destination terminal area; and an instrument approach guides it towards a runway, landing decision or missed approach.

Within our Aviation & Real-World Flying guidance, these are separate procedure types, not interchangeable names. One IFR flight may use all three; another may depart on vectors, join an arrival part-way through or receive a visual approach instead of an instrument approach procedure.

SID vs STAR: what is the difference in aviation?

A SID is an outbound departure procedure, while a STAR is an inbound arrival procedure.

The expansion of STAR causes occasional confusion. ICAO terminology uses standard instrument arrival, while US FAA material uses Standard Terminal Arrival Route. Both describe the published IFR arrival routing commonly called a STAR.

A SID should not be confused with every possible departure instruction. Airports may also use radar vectors, direct clearances or separately labelled obstacle-departure procedures, depending on the state and its procedure system.

How do SIDs, STARs and approaches fit together?

The normal sequence is departure, en-route flight, arrival and approach, although ATC can shorten, replace or vector between any of these stages.

Runway → SID → en-route route → STAR → transition or vectors → instrument approach → landing or missed approach

A SID may contain runway and en-route transitions, altitude constraints, speed limits, minimum climb gradients and equipment requirements. Some requirements protect against terrain or obstacles; others organise traffic. Seeing the procedure in an FMS does not establish that the aircraft can meet its performance requirements.

A STAR funnels traffic from one or more en-route entry points towards an airport. It may finish at an initial approach fix, feed an approach transition or terminate where controllers normally issue vectors. Published levels and speeds help create an orderly flow, but their presence on the chart is not automatically a clearance to descend.

An instrument approach normally contains initial, intermediate, final and missed-approach segments, although the precise arrangement varies. Common examples include ILS, localiser, RNAV or GNSS, RNP, VOR and, where still published, NDB approaches. Our practical explanation of flying SIDs and STARs covers procedure briefing, transitions and aircraft guidance in more detail.

Is a STAR the same as an instrument approach?

No. A STAR delivers arriving traffic into the terminal area; an instrument approach takes the aircraft from an approach entry point towards a landing or missed-approach decision.

A STAR may connect neatly to an approach, but it need not do so. ATC may provide vectors between them, clear the aircraft directly to an approach fix or assign a different arrival after a runway change. Likewise, an aircraft can fly an instrument approach without having flown a STAR.

Loading an approach in the FMS does not clear the aircraft to fly it. It also does not guarantee an automatic capture of the final course or glidepath. The correct navigation source, active leg and lateral or vertical mode still have to be selected according to the aircraft system.

The approach chart provides courses, altitudes, frequencies where applicable, minima and the missed-approach procedure. If these fields are unfamiliar, our guide to interpreting an instrument approach chart explains each procedure segment and minimum.

How do you choose the correct SID, STAR and approach?

Choose each procedure by runway, route continuity, aircraft capability, charted restrictions and ATC clearance, not simply by selecting the first name offered by the flight planner.

Our detailed procedure-selection guidance for a flight plan covers the full decision process. The essential checks are:

1. Determine the runway and airport configuration. Wind, traffic flow, runway availability and suitable approaches influence the expected runway. A departure runway change can require another SID; an arrival runway change can alter both the STAR transition and approach.
2. Match the route transition. Select a SID that leads towards the first useful en-route fix and a STAR whose entry transition connects with the final part of the route. Avoid adding the same transition fix twice, which can create loops or route reversals.
3. Check aircraft capability and performance. Confirm required navigation equipment, RNAV or RNP capability, radio aids, climb gradients and any aircraft restrictions. Database availability is not proof of operational eligibility.
4. Verify the procedure against the chart. Compare the exact procedure name, runway, transition, route legs, constraints and notes. Our guide to reading SID and STAR charts in a simulator shows how to cross-check them against the FMS.
5. Confirm the approach is usable. Check runway alignment, navigation equipment, minima, missed-approach routing and any operational limitations. Select an approach based on the conditions and clearance, not merely because the runway number matches.
6. Apply the clearance. Filing or programming a procedure is not permission to fly it in real-world IFR operations. The ATC clearance and applicable local rules determine what is authorised.

Do all charted altitude and speed restrictions apply?

Treat published restrictions as operative unless the clearance and applicable rules modify them, but distinguish mandatory constraints from advisory or expected values. Vertical authority depends on the procedure, jurisdiction and exact ATC phraseology.

• Lateral and vertical clearance are not identical. Clearance along a SID or STAR does not universally authorise every published climb or descent. Terms such as “climb via” and “descend via” carry defined meanings where those phrases are used.
• Constraint type matters. An altitude can be mandatory, at or above, at or below, inside a window, or included for planning rather than compliance. Read the chart legend and procedure notes rather than treating every printed number alike.
• Climb gradients require a performance check. A SID can demand more than the standard climb assumption. Aircraft weight, temperature, pressure altitude, wind and engine performance may decide whether it can be flown safely.
• Speed constraints are separate from FMS predictions. A predicted speed is not necessarily a charted restriction. Conversely, a mandatory speed does not disappear because the automation fails to command it.
• Approach minima are limits, not targets to ignore. At a decision altitude or height, initiate the missed approach when the required visual reference is unavailable or a safe landing cannot be continued. On a procedure using a minimum descent altitude or height, remain at or above it and observe the published missed-approach point.

If a real-world instruction is unclear or appears to conflict with the chart, pilots query ATC rather than guessing.

Can you fly a SID, STAR or approach without ATC in a simulator?

Yes, these procedures can be flown offline for simulator practice, provided you deliberately self-assign the runway, procedure, transition and vertical clearances.

Problems arise when built-in ATC instructions and a self-selected procedure are combined without resolving conflicts. Decide whether the exercise follows ATC or the chart. If the STAR terminates in vectors, do not invent a route across terrain or join final from an unstable position; set up a sensible intercept or practise from a known approach fix.

Real-world IFR operations are different. A programmed or filed SID, STAR or approach is not a clearance, and pilots must follow the assigned procedure and controller amendments.

Why does a SID, STAR or approach fail in a flight simulator?

Most simulator failures come from the wrong transition, mismatched navigation data, an intentional route discontinuity or guidance modes that were loaded but never activated.

• The route contains a loop or dog-leg. Check whether the selected transition returns to a fix already present in the en-route plan. Remove the duplicate route segment or select the transition that actually joins the route.
• The chart and database disagree. Procedure names, waypoints and restrictions change between AIRAC cycles. When practising a specific published procedure, use chart and navigation data from the same cycle where possible.
• A discontinuity was deleted without checking it. Some gaps represent expected radar vectors, a manual-termination leg or a genuine break between procedures. Do not connect every discontinuity automatically.
• Vectors-to-final removed useful legs. A vectors shortcut can discard initial or intermediate approach fixes. Use it only when vectors are actually intended; otherwise load the full transition.
• The procedure is loaded but not active. Confirm the active leg, navigation source and lateral mode. For an ILS or similar approach, check the required radio tuning and approach mode; for an RNAV procedure, verify that the aircraft is following the intended FMS path.
• VNAV cannot satisfy the profile. Arriving too high or fast can make a STAR or approach constraint impossible even when the route is correct. Reduce energy earlier rather than assuming the automation will recover an infeasible descent.
• A runway change left stale data. Recheck the STAR transition, approach transition, final course, frequencies, minima and missed approach after changing the runway.
• Simulator ATC conflicts with the programmed procedure. Built-in ATC may issue vectors or altitudes that do not match the loaded route. Follow the chosen training objective consistently instead of silently mixing incompatible instructions.