FAR Ninety-One One Seventeen, the Aircraft Speed Limits, and Why Two Hundred Fifty Knots Below Ten Thousand Is the Rule Every Pilot Quotes and Almost Nobody Reads All the Way Through

Federal Aviation Regulation 91.117 limits aircraft to 250 knots indicated airspeed below 10,000 feet MSL - but that’s only the first of four parts. The rules most pilots actually risk breaking are the 200-knot limits that apply beneath Class Bravo shelves and near Class Charlie and Delta airports. Understanding all four parts, and the fact that every limit is measured in indicated airspeed, is what separates reciting the rule from actually flying it.

What Does FAR 91.117 Actually Say?

The regulation has four parts, and most pilots only know the first one.

Part A: Below 10,000 feet MSL, you may not exceed 250 knots indicated airspeed. This is the headline number everyone quotes.

Part B: Within the surface area of Class Charlie or Class Delta airspace, at or below 2,500 feet AGL, and within 4 nautical miles of the primary airport, you may not exceed 200 knots.

Part C: Beneath a Class Bravo shelf, or transiting a published VFR corridor through the Bravo, you also may not exceed 200 knots.

Part D: If the minimum safe speed for a particular operation is greater than any of these limits, you may fly at that minimum safe speed. The rule will never force you to fly slower than is safe for your aircraft.

Why the 250-Knot Rule Barely Matters in a Trainer

If you fly a Cessna 172 or a Piper Cherokee, the 250-knot limit is almost meaningless. You physically cannot get a trainer to 250 knots in level flight - you could point the nose down and still likely never break it.

That’s why many student pilots read Part A, decide the whole regulation is somebody else’s problem, and move on. That’s a mistake. The other three parts are exactly the ones that catch light aircraft.

Which Speed Limits Actually Apply to General Aviation Pilots?

The 200-knot limits in Parts B and C are the ones you can realistically violate - and the ones designed to protect you.

Look at where they live: beneath a Bravo shelf, and down low near a Charlie or Delta field. These are the most congested, compressed pieces of airspace in the system. Airliners are descending, students are doing pattern work, a flight of two is departing, and someone’s shooting an instrument approach. The FAA drew a slower limit around exactly those places because that’s where aircraft get close to each other.

Who actually breaks the 200-knot rule? Usually not the trainers. It’s the faster GA airplanes - a Cirrus, a Bonanza, a Mooney, a twin, or a turboprop. These cruise at 160 to 190 knots true, and in a descent, indicated airspeed climbs. Point a fast single at the runway to lose altitude, let the speed build because it feels efficient, and you can slide past 200 knots indicated beneath a Bravo shelf without ever touching the throttle. It isn’t aggression - it’s a descent, gravity, and eyes fixed on the runway instead of the airspeed indicator.

Why Does “Indicated” Airspeed Matter So Much?

Every limit in 91.117 is measured in indicated airspeed - the number on the dial in front of you. Not true airspeed. Not groundspeed.

This matters because as you climb, true airspeed runs ahead of indicated. In thin air at altitude, a given indicated airspeed means a higher true speed across the ground. An airliner leveling at 9,500 feet showing 250 on the indicator is actually moving faster than 250 knots over the ground - but the regulation only cares about the indicated number.

Examiners love this point. Knowing the limit is indicated airspeed, knowing the three speed regimes, and being able to point at a sectional and say where each applies is the whole game. Not recitation - application.

How Do You Avoid Busting the 200-Knot Limit on Arrival?

Picture a Cirrus SR22 cruising home at 8,500 feet, headed to a busy Class Delta field that sits beneath a Class Bravo shelf - a classic setup near any major metro.

You start your descent 30 miles out. You pull a little power, push the nose over, and indicated airspeed creeps up: 180, 190, 200, 210. The airplane’s happy and you’re making great time.

The moment you slid beneath that Bravo shelf, your limit became 200 knots - and you’re doing 210 in the descent without noticing, because your eyes are outside. Get closer, within 4 miles of the Delta primary airport and below 2,500 feet AGL, and the limit is still 200 knots. You’ve now violated two parts of the same regulation on a single arrival.

The fix costs you nothing:

1. Pull the power earlier. Plan the descent so speed bleeds off before you reach the busy air, not after.
2. Glance at the airspeed indicator any time you’re descending toward a Bravo shelf or a Charlie/Delta field.
3. Ask one question: “Am I under 200?” One glance, one question. That’s the whole discipline.

Where Do the 200-Knot Limits NOT Apply?

This subtlety catches even experienced pilots. The 200-knot restriction lives in specific places - and lifts in others.

Beneath a Bravo shelf: 200 knots. But above the shelf, out in the clear, you revert to the general rule - 250 below 10,000.

Inside the Bravo itself: once you’re cleared in and talking to approach, there is no 200-knot general limit. You’re back to 250 below 10,000, because ATC is now sequencing you and providing separation.

The pattern is logical: the slowdown applies beneath the Bravo and around the smaller fields - precisely where no one is separating VFR traffic for you. The regulation puts the brakes exactly where you’re on your own and lets you speed up where a controller has your back.

Can ATC Authorize You to Exceed the Speed Limit?

No. You’ll sometimes hear a controller ask an airliner to “keep the speed up” - say, 250 to the marker. A controller cannot waive 91.117. There is no controller override for the speed limit the way there is for some other rules.

If you’re assigned a speed that would exceed the limit, the correct response is one word: “Unable.” You hold the certificate, and that regulation is yours to comply with - not the controller’s to lift.

The only relief valve is Part D, written into the rule itself: if safe operation requires a higher speed, you fly the safe speed. That’s for the airplane that can’t be flown slower - a heavy jet on approach, a formation flight, a warbird that stalls at 120 - not for the pilot who simply doesn’t want to slow down.

Why This Rule Matters Even If You Fly Slow

The speed limit is a see-and-avoid rule wearing a number. It exists to keep the closure rate between two aircraft low enough that a human has time to see, react, and survive.

Even if you’ll never overspeed a 172, you share airspace with airplanes that can. When you know everyone down low near a busy field is legally held to 200 knots, you understand the closure math: the fastest legal airplane and you are never closing at more than a couple hundred knots. That margin buys you the seconds to see and avoid. When someone breaks the rule, they aren’t just risking a phone number - they’re eating into the time margin that prevents a mid-air.

Key Takeaways

• The 250-knot limit applies below 10,000 feet MSL, but it rarely constrains light trainers that can’t reach that speed.
• The 200-knot limits are the ones GA pilots actually break - beneath a Bravo shelf (Part C) and within 4 NM and 2,500 feet AGL of a Charlie or Delta primary airport (Part B).
• Every limit is indicated airspeed - the number on your dial, not your true airspeed or groundspeed.
• ATC cannot waive 91.117. If assigned an illegal speed, respond “unable.” Only Part D (minimum safe speed) permits exceeding a limit.
• If you fly something fast, manage your descent early so speed is already down before you reach congested airspace.