FAR Ninety-One Point One Seventeen, the Speed Limit Regulation Students Learn in Half, and the Two Hundred Knot Rule That Hides in the Airspace Beneath Class Bravo

FAR 91.117 contains three distinct speed limits. Every pilot learns the headline - 250 knots below 10,000 feet MSL - but the same regulation imposes a 200-knot limit in two additional situations that catch even experienced pilots off guard. Understanding all three paragraphs is essential for flying in and around terminal areas legally.

What Does “Operate” Actually Mean Under FAR 91.117?

Paragraph A reads: No person may operate an aircraft below 10,000 feet mean sea level at an indicated airspeed of more than 250 knots.

The operative word is operate - not cruise, not maintain level flight. Climbs, descents, maneuvering, and pattern work all count. There is no phase of flight below 10,000 MSL where the two-fifty limit doesn’t apply.

The altitude reference is MSL, set to your local altimeter setting - not above ground level. Flying over mountainous terrain with the ground at 8,000 feet and your altimeter reading 9,500 feet MSL? The 250-knot limit still applies. The regulation has no interest in your terrain clearance - only what your altimeter reads.

The speed reference is indicated airspeed, not true airspeed and not GPS groundspeed. On a warm day at 9,500 feet MSL, your true airspeed may run 15–20 knots faster than indicated. If your airspeed indicator reads 248, you are legal under Paragraph A regardless of what your GPS says.

The 200-Knot Rule Near Class Charlie and Class Delta Airports

Paragraph B imposes a tighter limit in specific terminal environments: No person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class Charlie or Class Delta airspace area at an indicated airspeed of more than 200 knots.

Two conditions must be true simultaneously. You must be within 4 nautical miles of the primary airport, and you must be at or below 2,500 feet AGL. Either condition alone is not enough - both must apply at the same time to trigger the 200-knot limit.

Note the altitude reference shift: Paragraph B uses AGL, not MSL. If the primary airport sits at a field elevation of 800 feet, the 2,500-foot ceiling under Paragraph B sits at 3,300 feet MSL. The surface reference anchors to the terrain.

The reasoning is practical. Within 4 miles of a Class C or D airport, you have approach corridors, pattern traffic, and student pilots on their first solo cross-country - traffic that is slow, maneuvering, and not always predictable. Two hundred knots is still genuinely fast in that environment. Reaction time matters.

The Class Bravo Underlying Airspace Rule - The One That Catches Pilots

Paragraph C is the least-known and most consequential: No person may operate an aircraft in the airspace underlying a Class Bravo airspace area, or in a VFR corridor designated through such a Class Bravo airspace area, at an indicated airspeed of more than 200 knots.

The critical word is underlying. This means the airspace beneath the Bravo shelf - outside the Bravo boundary, below its floor. You never entered Class Bravo. You never needed a clearance. Paragraph C still applies to you.

Take the Chicago O’Hare Class Bravo as an example. In different rings, the Bravo floor sits at different altitudes - perhaps 3,000 MSL in one sector, 4,000 or 5,000 MSL in another. A VFR aircraft at 2,800 feet MSL under a shelf that starts at 3,000 feet is in the underlying airspace. No Bravo frequency contact required, no Bravo clearance needed - and a 200-knot maximum in effect.

Here is where the conflict with Paragraph A creates confusion. Paragraph A says 250 knots below 10,000 MSL, and it technically applies everywhere below 10,000. But Paragraph C says 200 knots in the underlying airspace. The most restrictive applicable limit always governs. Two hundred wins.

VFR Corridors Are Not Speed Exemptions

Some Class Bravo designs include VFR corridors - carved-out slices that allow aircraft to transit without holding a clearance. The Los Angeles Class Bravo has corridor structures commonly used to transit the basin without contacting approach control.

Flying through a VFR corridor means flying through what would otherwise be Class Bravo airspace, but without the clearance requirement. Paragraph C still applies inside the corridor. The corridor grants passage - not a speed exemption.

What Changes Once You Receive a Class Bravo Clearance

Once ATC clears you into Class Bravo, you are no longer in the underlying airspace - you are inside the Bravo itself. Paragraph C’s underlying airspace language no longer applies.

At that point, only Paragraph A governs your speed unless ATC assigns a specific speed explicitly. If you are at 8,000 MSL inside the Bravo with a clearance and no speed assignment from ATC, your ceiling is 250 knots, not 200.

The sequence: below the Bravo floor without a clearance = 200 knots. Inside the Bravo with a clearance and no ATC speed assignment = 250 knots. ATC assigns a specific speed = fly the assigned speed, which takes precedence over both.

What Paragraph D Actually Means - And What It Doesn’t

Paragraph D states that if the minimum safe airspeed for a particular operation exceeds the maximum prescribed in the section, you may operate at that minimum speed.

This is not a general aviation loophole. It exists for heavy transport category aircraft on certain approach configurations whose minimum controllable speeds can exceed typical GA speed limits. Forcing such an aircraft below its minimum controllable speed would create a greater hazard than the speed limit it would violate.

For pilots flying normal GA singles and light twins, this exception does not apply. Your aircraft can operate safely well below 200 knots.

A Practical Speed Framework for Terminal Area Flying

Above 10,000 MSL: No regulatory speed limit from FAR 91.117 - fly to your airplane’s performance limits.

Below 10,000 MSL: 250 knots maximum (Paragraph A, indicated airspeed).

Underlying Class Bravo airspace or VFR corridor: 200 knots maximum (Paragraph C), regardless of whether Paragraph A’s 250-knot limit is also technically in effect.

Within 4 NM of a Class C or D primary airport at or below 2,500 AGL: 200 knots maximum (Paragraph B).

Multiple paragraphs in effect simultaneously: The most restrictive limit governs. Always.

One additional discipline worth building early: plan your speed management before reaching a restricted airspace boundary, not as you cross it. The regulation requires that you not operate in that airspace above the applicable limit - meaning you need to already be at or below the speed when you enter, not in the process of decelerating as you arrive.

Key Takeaways

• FAR 91.117 contains three speed limits, not one. The 250-knot rule is Paragraph A. Two additional 200-knot limits exist in Paragraphs B and C.
• “Operate” means all phases of flight - climbs, descents, and maneuvering count, not just cruise.
• Paragraph C’s 200-knot limit applies in the airspace underlying Class Bravo, even if you never enter the Bravo and never contact its facility.
• Once cleared into Class Bravo, Paragraph C no longer applies - Paragraph A’s 250-knot limit governs unless ATC assigns a specific speed.
• The most restrictive applicable limit always wins when multiple paragraphs apply simultaneously.