FAR Ninety-One Point One Seventeen, the Speed Limit Below Ten Thousand, and the Two-Hundred-Knot Rule That Catches Every IFR Student Off Guard

FAR 91.117 governs aircraft speed limits in the National Airspace System and contains more layers than most pilots realize. The familiar 250-knot rule below 10,000 feet is just the foundation - additional limits apply inside Class Delta, Class Charlie, and beneath Class Bravo, and one provision in particular catches IFR students off guard on checkrides.

Why Does This Regulation Exist?

The speed limits in FAR 91.117 trace back to a genuine safety problem in the late 1950s and early 1960s. As commercial jet aviation expanded, military jets and airliners operating in the lower altitude bands shared the same airspace as general aviation piston aircraft. A Boeing 707 on descent could be doing 400 knots. A Piper Cherokee in the pattern was doing 90. The closing speeds between those aircraft were enormous, and the separation margins controllers needed were collapsing faster than the technology could manage.

The FAA’s solution was to create a speed limit for the lower altitude environment - a band below 10,000 feet MSL where traffic density is highest and where general aviation and commercial aviation share the most airspace. Cap the speeds in that band, and the differentials become manageable. Controllers can vector and sequence. Slower aircraft have a fighting chance.

What Is the Speed Limit Below 10,000 Feet?

Below 10,000 feet MSL, no pilot may operate at an indicated airspeed greater than 250 knots. This applies everywhere below that altitude - no exceptions for aircraft type, no exceptions for airspace class.

For most student pilots in the piston fleet, this number is theoretical. A Cessna 172 at full throttle near sea level tops out around 120 knots indicated. But as you move into more capable training aircraft and begin flying IFR into busier terminal environments, that ceiling becomes something you actively manage in real time.

One critical point: 250 knots is a maximum, not a target. If conditions, traffic density, or ATC instructions require a lower speed, that lower speed is the right answer.

What Is the Speed Limit in Class Delta Airspace?

Inside Class Delta airspace, the limit drops to 200 knots indicated - 50 knots below the general 10,000-foot rule.

Class Delta typically extends from the surface to approximately 2,500 feet above airport elevation, usually within a 4-to-5 nautical mile radius around a towered airport. Inside that environment, a controller is managing a mix of aircraft: students doing touch-and-gos, corporate traffic, helicopters, and potentially a dozen training aircraft in the pattern simultaneously. Entering that environment at 249 knots would be technically legal under the 10,000-foot rule but would make safe sequencing with slower traffic ahead effectively impossible.

The 200-knot limit forces everyone into a speed regime where the controller’s job is actually manageable.

What Is the Speed Limit in Class Charlie Airspace?

The surface area of Class Charlie airspace carries the same limit: 200 knots indicated. Class Charlie airports are busier still - regional commercial hubs with a mix of airline traffic, corporate aircraft, general aviation, and often nearby flight training operations.

But here is the provision that trips up IFR students on checkrides: the 200-knot limit for Class Charlie extends beyond the charted surface area.

Within 4 nautical miles of the primary airport of a Class Charlie, from the surface up to 2,500 feet above the airport elevation, the 200-knot limit applies - whether or not you have entered the charted surface area, whether or not you are in contact with approach, and whether or not approach has issued any speed instruction.

The FAA wrote it this way because the traffic conflict in the approach environment does not wait for you to cross a line on a sectional chart. Converging traffic exists well before you formally enter any charted boundary.

What Are the Speed Limits Near and Under Class Bravo Airspace?

FAR 91.117 includes two provisions specifically for Class Bravo environments.

At or below 2,500 feet above an airport beneath Class Bravo: If you are operating at or below 2,500 feet above the field elevation of an airport that lies underneath Class Bravo airspace, the speed limit is 200 knots. Major Bravo airports have numerous smaller general aviation fields and busy VFR corridors underneath their floors, and those environments need the same speed protection.

In designated VFR corridors through Class Bravo: These corridors also carry a 200-knot maximum. Defined passages through complex airspace need to be consistent, predictable environments for all users.

How Do the Speed Limits Play Out on an IFR Arrival?

A practical scenario shows exactly where and when each limit applies.

You are flying a Piper Seneca on an IFR flight plan arriving at a Class C airport. You are level at 8,000 feet MSL - already below 10,000, so the 250-knot limit is in effect. You are indicating 230 knots. Legal.

Approach descends you to 5,000 feet and vectors you for the ILS. You are 12 nautical miles from the airport and above 2,500 feet above field elevation. The 4-nautical-mile provision is not yet a factor. Indicating 210 knots. Legal.

You continue descending to 4,000 feet, 7 nautical miles from the airport, still outside the 4-mile ring. Indicating 210 knots. Legal.

You pass inside the 4-nautical-mile ring from the primary airport and descend through 2,500 feet above field elevation. The 200-knot limit now applies. If you are still indicating 210 knots at this point, you are in violation - regardless of whether approach issued any speed instruction.

No one from ATC told you to slow down. The regulation applies based on where you are, not on what you were told. This is exactly the scenario an instrument examiner may walk through in an oral, looking for a pilot who can identify the precise point where the speed limit changes and articulate why.

Can ATC Override the Speed Limits in FAR 91.117?

ATC cannot authorize you to exceed the regulatory speed limits. If a controller issues a speed assignment that would require you to violate the regulation, the correct response is to advise them you cannot comply: “Unable, the speed limit in this airspace is 200 knots.” Controllers are generally well aware of these limits, but the regulation governs - not the clearance.

The reverse is always permissible: ATC can assign a speed more restrictive than the regulatory limit at any time. If approach assigns 160 knots on final, comply. The regulation sets the maximum; ATC can always require less.

How to Build Speed Limits Into Your Pre-Arrival Brief

The pilots who get caught by these limits are almost always the ones working through the logic for the first time at a busy moment - on a descent, with approach in one ear and a checklist in the other.

Before any arrival into Class C or B airspace, know:

• The dimensions of the airspace you are entering
• Where the 4-nautical-mile ring from the primary Class Charlie airport falls relative to your expected arrival vectors
• At what point in your descent the 200-knot limit applies, based on field elevation and distance from the primary airport

Build that picture into your pre-arrival brief on the ground. It takes 30 seconds when you are not under pressure, and it means you will never be working out the logic in real time on a descent.

Key Takeaways

• Below 10,000 feet MSL: 250 knots indicated maximum - no exceptions for aircraft type or airspace class
• Inside Class Delta and Class Charlie surface areas: 200 knots indicated maximum
• Within 4 NM of a Class Charlie primary airport, below 2,500 feet above field elevation: 200 knots - applies whether or not you have entered the charted surface area
• Beneath Class Bravo (at or below 2,500 feet above underlying airports) and in VFR Bravo corridors: 200 knots
• All limits are indicated airspeed - not true airspeed, not groundspeed
• Speed limits are maximums, not targets - always operate at whatever speed conditions require