What is the difference between a mandatory crossing restriction and an expected crossing restriction on a STAR?

A mandatory crossing restriction, depicted on a chart with an underline and/or overline around the altitude (or both for an 'at' restriction), is a hard altitude that ATC expects you to cross at exactly as charted or as amended by ATC. An expected crossing restriction, shown without those lines, is an advisory altitude that ATC anticipates issuing but may adjust, so you should not fly it unless ATC actually assigns it in your clearance. The PHAK and AIM both emphasize that pilots must comply with mandatory altitudes unless ATC issues a specific amended clearance.

How do you identify a mandatory crossing altitude versus an MEA on a STAR procedure chart?

A mandatory crossing altitude on a STAR is printed with a line above it, below it, or both (indicating 'at or above,' 'at or below,' or 'at,' respectively) and applies to a specific fix. An MEA (Minimum En Route Altitude) represents the lowest published altitude between fixes that ensures obstacle clearance and, on applicable routes, navigation signal reception, but it is not a crossing restriction at a fix. According to the Instrument Flying Handbook, pilots must distinguish these two types because the MEA is a floor for en route segments, while mandatory restrictions are ATC-controlling altitudes at specific points.

Why do crossing restrictions on STARs matter for ATC clearances during the FAA Instrument Rating Airplane Airmen Certification Standards?

The FAA Instrument Rating Airplane Airmen Certification Standards (ACS) requires applicants to demonstrate the ability to correctly interpret and comply with arrival procedure crossing restrictions because busting a mandatory altitude constitutes a deviation from an ATC clearance and can result in a loss of separation. Mandatory restrictions printed on a STAR become part of your clearance the moment ATC issues 'cleared for the STAR,' so no additional verbal instruction is required to make them binding per the AIM. Understanding the difference between mandatory, expected, and MEA altitudes ensures you neither climb or descend prematurely nor miss a required altitude at a charted fix.

Crossing Restrictions: Mandatory vs. Expected vs. MEA on STARs

When you fly an instrument approach into a busy terminal environment, the Standard Terminal Arrival Route (STAR) is your roadmap from the enroute structure down to the initial approach fix. But a STAR is more than a line on a chart — it's loaded with crossing restrictions that tell you exactly where to be and at what altitude, speed, or combination of both. Knowing the difference between a mandatory restriction, an expected restriction, and a minimum enroute altitude (MEA) isn't just a test question; it's the legal and operational foundation for flying a STAR correctly and safely.

This article breaks down each restriction type in plain English, explains the symbology you'll see on Jeppesen and National Aeronautical Charting Office (NACO/FAA) charts, and gives you the mental framework to apply them the moment ATC clears you for the arrival.

What Is a STAR and Why Do Restrictions Exist?

A STAR, defined in the Instrument Procedures Handbook (FAA-H-8083-16), is an ATC-designed procedure that transitions arriving IFR traffic from the enroute phase to the terminal area in an orderly, predictable way. Because a STAR is published and standardized, controllers can issue a single clearance — "Cleared the HAWKZ ONE arrival" — and know exactly where you'll be at each fix, provided you fly the published restrictions. Crossing restrictions exist to maintain vertical separation between aircraft on the same or converging arrivals, to keep aircraft clear of terrain and obstacles, and to sequence traffic for the approach phase.

The Three Types of Restrictions

Mandatory Crossing Restrictions

A mandatory restriction means you must cross a specific fix at the published altitude, speed, or both — no earlier, no later, no higher, no lower. On FAA (NACO) charts, a mandatory altitude is depicted underlined and overlined simultaneously: a line both above and below the altitude value. On some charts it appears inside a box. This double-line or box treatment is your visual cue that the restriction is non-negotiable unless ATC explicitly amends it with a specific clearance.

For example, if a fix shows "11,000" with lines above and below, you must cross that fix at exactly 11,000 feet MSL. If ATC says "descend and maintain 9,000" and you're still inbound to that fix, the new ATC clearance supersedes the published restriction for that descent — but only because a controller has assumed responsibility for your separation. Without an amended clearance, the published mandatory restriction stands and is part of your ATC clearance the moment the STAR is included in it.

Speed restrictions work the same way. A mandatory speed of 250 knots indicated (KIAS) underlined and overlined means cross that fix at exactly 250 KIAS. If the chart shows "AT OR BELOW 250 KIAS," that is a ceiling, not a point value — you may be slower, but not faster.

Expected (or "Expect") Restrictions

Expected restrictions are planning values — altitudes or speeds that ATC anticipates assigning but has not yet formally cleared you to fly. The key word is expect. On an arrival chart you might see a note such as "Expect to cross FIXNAME at or above FL240" or "Expect 250 knots by WAYPOINT." These restrictions matter most in two contexts:

Contingency planning: If radio communication is lost, 14 CFR 91.185 directs you to fly the highest of the last assigned altitude, the minimum altitude for IFR operations, or the altitude ATC told you to expect. An expected altitude on a STAR is exactly that — the altitude you would use to continue in NORDO (no radio) conditions.
Descent planning: Even in normal operations, "expect" altitudes let you brief a top-of-descent point and calculate your required vertical speed before ATC formally clears you lower.

Critically, an expected restriction does not authorize you to leave your assigned altitude. You must hold your last cleared altitude until ATC gives you a new clearance, even if the STAR says "expect 8,000 by FIXNAME." This distinction trips up many students on the written exam.

Minimum Enroute Altitude (MEA) on STARs

The MEA is the lowest published altitude for an IFR segment that guarantees both obstacle clearance and, in most cases, acceptable navigation signal reception. On a STAR, MEAs appear along route segments between fixes, not at fixes themselves — they define a floor for that segment of flight. The MEA does not require you to fly at that altitude; it simply prohibits you from flying below it on that segment unless you have an ATC clearance to a lower altitude and terrain and obstacle clearance are otherwise assured by the controller.

You'll also encounter the Minimum Obstruction Clearance Altitude (MOCA) on some segments, depicted with an asterisk (e.g., "*7,400"). The MOCA guarantees obstacle clearance but only guarantees navigation signal reception within 22 nautical miles of a VOR. On a GPS-based STAR, the navigation signal concern is less relevant, but obstacle clearance remains critical.

On STARs, MEAs are particularly important when the filed or ATC-assigned altitude is near or at the MEA — descending below it without authorization is a potential controlled flight into terrain (CFIT) scenario. Always compare your cleared altitude against the MEA for the segment you're flying.

Chart Symbology: Reading the Difference at a Glance

FAA/NACO chart convention uses a straightforward visual coding system for altitude restrictions:

Overline AND underline (or boxed): Mandatory — cross AT this altitude.
Overline only: "At or above" — cross at or higher than this altitude.
Underline only: "At or below" — cross at or lower than this altitude.
No line: The altitude is a recommended or planning value — not a regulatory restriction unless the chart notes otherwise.
MEA along a segment: Appears as a simple altitude number adjacent to the airway or route segment, often with the airway identifier.

Jeppesen charts use slightly different graphical conventions but convey the same information — always know which chart format you're using and check the chart legend if any symbol is unfamiliar.

Why It Matters: Legal Authority and Safety

Once ATC issues a clearance that includes a STAR, the published restrictions become part of your clearance under 14 CFR Part 91. Flying through a mandatory restriction without authorization is a deviation from your ATC clearance — a potential violation and, more importantly, a separation risk with other traffic. ATC spaces aircraft vertically and laterally based on the assumption that every pilot on the arrival is crossing those mandatory fixes exactly as charted.

Expected restrictions matter most if radio communications fail. Under 14 CFR 91.185, a pilot who loses two-way radio communication in IFR conditions must fly the expected altitude to give ATC a predictable picture of where that aircraft will be, enabling controllers to protect the airspace accordingly.

MEAs protect you from the ground. In mountainous terrain, the MEA on an arrival segment may be thousands of feet above sea level. Accepting a lower clearance than the MEA in an area of poor radar coverage without full situational awareness of terrain is one of the leading CFIT scenarios.

Key Numbers and Rules

A mandatory restriction (both lines or box) must be complied with exactly — at that altitude or speed — unless ATC amends it verbally.
An "at or above" restriction (overline only) sets a floor; you may be higher but not lower.
An "at or below" restriction (underline only) sets a ceiling; you may be lower but not higher.
An "expect" restriction does not authorize a deviation from your last cleared altitude.
For NORDO, 14 CFR 91.185 requires flying the highest of: last assigned altitude, minimum IFR altitude, or altitude ATC said to expect.
The MEA guarantees obstacle clearance for the entire segment and, on VOR airways, nav signal reception; it is a floor, not a target altitude.
MOCA (asterisked altitude) guarantees obstacle clearance but ensures VOR reception only within 22 NM of the station.

Memory Aid

For crossing restriction symbology, use the phrase "Over-Under Mandatory, Over-Only Above, Under-Only Below":

Over AND Under = Mandatory (AT this altitude)
Over-Only = At or Above (floor)
Under-Only = At or Below (ceiling)

This simple three-part rule lets you decode any altitude restriction on a U.S. instrument chart without having to reference the legend once it's memorized.

Common Test Traps

"Expect" means cleared: Many students read "Expect to cross at 10,000" and begin descending. An expect restriction is a planning value only — you need an ATC clearance before leaving your assigned altitude.
NORDO altitude selection: The exam frequently asks which altitude to fly after losing communications. The answer is the highest of the three options in 91.185 — not simply the last assigned altitude.
MEA vs. mandatory restriction: The MEA is a floor for the segment between fixes; a mandatory restriction applies at the fix itself. Students sometimes confuse a segment MEA with an "at" restriction at a waypoint.
Speed restrictions persist: A published mandatory speed restriction (e.g., 250 KIAS at a fix) remains in force as part of your clearance even if ATC says "descend to 8,000" — the speed restriction survives unless ATC explicitly cancels it.
Overline vs. underline direction: On a rushed check ride or exam, students swap the meaning of overline-only and underline-only. Remember: a line on TOP is a floor (at or above — the line is the ceiling of the airspace below you); a line on the BOTTOM is a ceiling (at or below).