What is the VFR cruising altitude rule in FAR 91.159?

FAR 91.159 requires VFR pilots in level cruise more than 3,000 feet above the surface to fly odd-thousand-foot MSL altitudes plus 500 feet when eastbound (magnetic course 0°–179°), and even-thousand-foot MSL altitudes plus 500 feet when westbound (magnetic course 180°–359°).

Does FAR 91.159 use magnetic course or magnetic heading?

The regulation specifies magnetic course - the intended ground track - not magnetic heading. On a windy day, heading differs from course due to wind correction, but altitude selection is always based on the magnetic course shown on the navigation log.

Why does the VFR cruising altitude rule add 500 feet to each altitude?

IFR traffic flies whole-thousand-foot altitudes (5,000, 6,000, etc.). The 500-foot offset places VFR traffic between IFR altitude assignments, creating a built-in vertical buffer. It also produces 1,000 feet of separation between opposite-direction VFR traffic flying adjacent altitudes.

Does FAR 91.159 apply in mountainous terrain at high MSL altitudes?

It depends on AGL clearance. The rule triggers above 3,000 feet above the surface, not above MSL. Flying at 10,000 feet MSL over terrain at 7,000 feet MSL puts you right at the 3,000-foot AGL threshold - check the actual AGL value along every leg of the route, not just the MSL altitude.

Does FAR 91.159 apply during night VFR flights?

Yes. The cruising altitude rule applies identically day and night. Terrain clearance becomes more critical after dark because terrain below is no longer visible, so consider adding margin above the regulatory minimum on night cross-country legs over high terrain.

FAR Ninety-One Point One Five Nine, the East-Is-Odd Rule Students Get Half Right, and the Three-Thousand-Foot Floor That Changes Everything About Cross-Country Altitude Planning

FAR 91.159 governs the altitude every VFR pilot must fly during level cruise more than 3,000 feet above the surface. The rule is commonly summarized as “east is odd, west is even” - but that shortcut leaves out two critical details that checkride examiners will probe directly.

What Does FAR 91.159 Actually Require?

When flying under visual flight rules in level cruising flight more than 3,000 feet above the surface, altitude selection is based on magnetic course:

Magnetic course 0° through 179° (eastbound): Fly any odd thousand-foot MSL altitude plus 500 feet - 3,500, 5,500, 7,500, 9,500 feet, and so on.
Magnetic course 180° through 359° (westbound): Fly any even thousand-foot MSL altitude plus 500 feet - 4,500, 6,500, 8,500 feet, and so on.

East is odd, west is even, and every valid altitude includes the plus 500 feet. Those are the three components. Leave any one out and the answer is incomplete.

Why Does the Rule Say “Magnetic Course” Instead of “Magnetic Heading”?

This distinction causes more checkride stumbles than any other part of the regulation, because course and heading feel interchangeable during early cross-country training - but they are two different numbers.

Magnetic course is the direction of intended ground travel: the line drawn on the chart from departure to destination. Magnetic heading is where the nose is pointed after applying a wind correction angle to compensate for drift.

On a calm day, they match. Add a 15-knot crosswind from the north on a due-east course of 090° and a wind correction angle of 5–6 degrees puts the heading at roughly 095° - but the course is still 090°. That course is what FAR 91.159 uses for altitude selection.

Write the magnetic course clearly for each leg of the navigation log. When an examiner asks why you selected 5,500 feet, the complete answer is: “The magnetic course on this leg is 085°, which falls in the 0° through 179° range, so I need an odd MSL altitude plus 500 feet.” That answer demonstrates understanding, not just a memory trick.

What Is the 3,000-Foot Floor in FAR 91.159?

The regulation’s trigger is more than 3,000 feet above the surface - not 3,000 feet MSL. This distinction matters most in mountainous terrain.

At 10,000 feet MSL over the Rockies where terrain sits at 7,000 feet, you are right at the 3,000-foot AGL threshold. One hundred feet lower and the rule no longer technically applies. The same 10,000-foot MSL altitude over the Great Plains, where terrain sits at 1,500 feet, puts you 8,500 feet AGL - well inside the rule’s scope.

For most cross-country flights over flat terrain at typical VFR cruising altitudes, the rule governs the entire route. In mountain flying or near high terrain, identify exactly where the 3,000-AGL threshold falls along your specific route.

The practical upside: the terrain-clearance analysis done during preflight planning also reveals when 91.159 kicks in. It’s the same work, giving two answers at once.

Why Do VFR Altitudes Include the Extra 500 Feet?

The +500 feet is not arbitrary - it’s a deliberate separation buffer between VFR and IFR traffic. IFR traffic flies whole-thousand-foot altitude assignments: 4,000, 5,000, 6,000 feet, with no half-thousand offset. Without the VFR offset, a VFR pilot at 5,000 feet eastbound could share an altitude with an IFR aircraft at 5,000 feet - different speeds, different equipment, no guaranteed awareness of each other.

The 500-foot offset creates a vertical buffer between VFR and IFR traffic in the same altitude band. VFR eastbound at 5,500 feet. IFR traffic at 5,000 or 6,000 feet - never at 5,500.

The scheme also addresses opposite-direction VFR traffic. Eastbound VFR at 5,500 feet and westbound VFR at 6,500 feet maintain exactly 1,000 feet of vertical separation, even when converging head-on at altitude. Build that into the traffic scan: when cruising eastbound at 5,500 feet, westbound traffic should be at 4,500 or 6,500 feet. Those are the levels to prioritize when scanning.

How Do Winds Aloft Factor Into Altitude Selection?

FAR 91.159 provides a range of compliant altitudes, not a single prescribed answer. Eastbound, the legal options include 3,500, 5,500, 7,500, and 9,500 feet, among others. Terrain clearance and airspace will eliminate some of those choices, but within the remaining legal options, winds aloft should drive the final selection.

Before any cross-country, pull the winds aloft forecast from the Aviation Weather Center. Forecasts are published at 3,000, 6,000, 9,000, 12,000, and 18,000 feet, among other levels. Compare those forecasts for your departure area, midpoint, and destination at each legal altitude.

If the forecast shows a 20-knot headwind at 5,500 feet but only a 10-knot headwind at 7,500 feet, climbing higher costs fuel on the way up but may save time and fuel in cruise on a long leg. 7,500 feet remains fully compliant - and may be the better choice. Regulation compliance is the floor, not the ceiling.

When Does FAR 91.159 Not Apply?

ATC altitude assignments override the rule. If a controller assigns an altitude that doesn’t conform to the VFR cruising scheme - common near Class Bravo or Class Charlie airspace where active traffic separation is in effect - fly the assigned altitude. When back in uncontrolled airspace and re-established in level cruise, return to the appropriate VFR altitude for the magnetic course.

The regulation also exempts holding patterns of two minutes or less and non-level flight. The rule applies specifically to “level cruising flight.” During climbs, descents, or turns, it doesn’t technically govern. The moment the aircraft rolls out and establishes cruise on the new heading, it applies again.

How Does FAR 91.159 Apply to Each Leg of a Multi-Leg Route?

Each leg with a different magnetic course is a separate altitude decision. Transitioning from a northeast leg to a southwest leg changes both the course direction and the altitude requirement. That transition needs to be planned on the ground, not sorted out in the air.

On the navigation log, the altitude column must reflect each leg individually. If every leg shows the same altitude regardless of course direction, that signals to an examiner that the regulation was treated as a one-time check rather than a per-leg planning requirement. Know when to initiate any required climb or descent between legs, and brief it before departure.

What Do Checkride Examiners Actually Look For?

The Private Pilot ACS cross-country planning task requires demonstrating that altitude selection accounts for four overlapping factors: terrain clearance, airspace restrictions, winds aloft, and FAR 91.159 compliance. All four feed a single number on the navigation log.

Examiners can distinguish a student who recites the regulation from one who applies it to a real route, real chart, and real terrain. The ability to walk through that reasoning clearly - citing magnetic course, identifying the applicable direction range, confirming terrain clearance, referencing the winds aloft forecast - demonstrates genuine understanding. That difference is apparent in about 30 seconds.

“East is odd, west is even, plus 500” is the starting point of the answer, not the whole answer.

Does FAR 91.159 Apply During Night VFR?

Yes. The cruising altitude rule applies identically day and night. VFR is VFR regardless of sunset, and the altitude requirements don’t change after dark.

Terrain clearance becomes more consequential at night because visual reference to terrain below disappears. Comply fully with 91.159 and then consider adding margin above the minimum terrain clearance on legs over terrain that can’t be monitored visually from the cockpit.

When Does FAR 91.159 Apply to Student Pilots?

From the first solo cross-country flight - defined as any flight more than 25 nautical miles from the home airport without an instructor aboard. Not from the private pilot certificate. From the first unaccompanied cross-country.

Solo cross-country endorsement preparation should include a direct conversation about FAR 91.159. If that conversation hasn’t happened, raise it before the flight.

Key Takeaways

FAR 91.159 applies above 3,000 feet AGL - above the surface, not above MSL - which matters significantly in mountainous terrain.
The rule uses magnetic course (your intended ground track), not magnetic heading, so wind correction angles don’t affect altitude selection.
The +500-foot offset separates VFR traffic from IFR whole-thousand-foot altitudes and creates 1,000 feet of vertical spacing between opposite-direction VFR traffic.
Each leg of a multi-leg route requires its own altitude decision based on that leg’s magnetic course - a single altitude for the whole route is a planning error.
ATC altitude assignments override the rule; return to the appropriate VFR cruising altitude when back in uncontrolled airspace and established in level cruise.