The first time you level off in a descent and consciously hold the speed back to 250 knots, you are obeying one of the most universal rules in the air. The speed limits at lower levels are simple to state but easy to muddle, especially where a tighter limit bites near busy airspace, so it is worth getting the layers straight.
This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.
Why low-level speed is capped
Below 10,000 feet is where the traffic mixes: fast aircraft, slow aircraft, and aircraft operating visually under VFR, all sharing the same air, where see-and-avoid has to work. Slowing everyone down gives more time to see, decide and avoid, and reduces the energy in any collision. That is the reasoning behind the basic limit, and it is why the rule lives at 10,000 feet, the level above which the traffic thins and oxygen requirements begin to limit who is there.
The 250-knot rule
The basic limit is the same on both sides of the Atlantic in substance, if not in wording:
- The FAA, in 14 CFR 91.117, prohibits more than 250 knots indicated below 10,000 feet MSL.
- EASA, in SERA.6001 of the Standardised European Rules of the Air, sets the same 250 knots indicated below FL100, drawing on ICAO Annex 2.
Both are written in indicated airspeed, so the figure you hold is the one on the airspeed indicator, regardless of the groundspeed the wind gives you. The EASA limit is set by airspace class and does not bite in the higher-level controlled airspace (Class A and B), where ATC manages speed directly, but for the lower airspace a private flight crosses it amounts to the same 250-knot ceiling below FL100.
The tighter 200-knot limits
The FAA rule then adds slower limits for the busiest low-level airspace:
- 200 knots indicated at or below 2500 feet above the surface within 4 nautical miles of the primary airport of Class C or Class D airspace;
- 200 knots indicated in the airspace beneath a Class B shelf or in a published VFR corridor through Class B.
There is one relief valve: if the minimum safe speed for the aircraft's configuration is higher than a limit, the aircraft may be flown at that minimum safe speed, and the crew should let ATC know.
A worked example
You are descending a fast aircraft toward a Class C airport. Passing 10,000 feet you bring the speed back to 250 knots indicated to satisfy the basic limit. Continuing down toward the field, you join the pattern below 2500 feet above the surface and inside 4 nautical miles of the primary airport, so now the 200-knot limit applies, and you slow again. None of this depends on the wind: a 40-knot tailwind might give you a groundspeed well above 250 knots while your indicated speed sits right on the limit, which is exactly what the rule intends.
In European airspace the first step is identical in effect: through FL100 you are held to 250 knots indicated under SERA.6001, with any further restrictions coming from the airspace and ATC.
Common pitfalls
- Indicated, not ground. A tailwind cannot bust the limit; the rule is on the airspeed indicator, not the GPS groundspeed.
- The 200-knot pockets are easy to forget. Near Class C and D airports and under Class B, the limit drops; plan the second speed reduction, not just the first.
- Minimum safe speed is the only relief. If your clean configuration needs more than the limit, you may use the minimum safe speed and tell ATC; it is not a general exemption.
In Pilot EFB
Pilot EFB is a study and planning companion for the airspace you will cross and the rules that go with it, alongside your weather, NOTAMs and flight time in one offline-first place. It does not monitor your speed or replace the regulations and your charts, so fly the published limits from your official source of record. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.