Heathrow doesn’t cap how many planes fly at night. It caps how much cumulative noise they may produce. The Quota Count system assigns every aircraft a noise value, from QC/0.125 up to QC/16, and each movement spends a slice of the season’s fixed noise budget.
Between 22:30 and 05:00, any aircraft rated QC/4 or higher is banned outright. QC/8 and QC/16 are barred for the whole night period. The practical result: airlines need quiet, modern aircraft to operate at all after 22:30.
Here’s what most travelers get wrong about Heathrow’s night rules: there is no blanket curfew. No one in the tower is counting planes like patrons at a club door. Instead, the airport rations something harder to see — the total acoustic energy its neighbours must absorb between dusk and dawn. The mechanism is the Quota Count system, a scale that grades aircraft from whisper-quiet QC/0.125 to thunderous QC/16. Every take-off and landing spends part of a seasonal noise allowance set by the Department for Transport. Some nights the movement count barely matters. What matters is which airframe the airline brought. A Boeing 787 can slot into the night schedule almost unnoticed. A 747-400 cannot — not because anyone hit a movement limit, but because the 747 carries a QC/4 rating, and QC/4 is banned in the night quota period. That binary rule, not a flight counter, is the real gatekeeper of Heathrow after dark.
The noise budget nobody sees
Two numbers govern Heathrow’s nights, and they pull in different directions. The first is a movement cap: 5,800 take-offs and landings across the year, split into 3,250 for summer and 2,550 for winter. That’s the number most coverage reaches for. But the second number is the one that actually decides which aircraft fly: 2,735 quota count units, the total noise budget for the summer season.
Since every movement spends QC value from that budget, a single loud departure can consume what would have covered dozens of quiet ones. Airlines don’t just need a movement slot — they need room inside the noise allowance too.
What the bans actually ban
QC/4 is the hard wall. According to NATS, any aircraft rated QC/4 may not take off or land during the night quota period (22:30–05:00). QC/8 and QC/16 are completely locked out for the entire night period (22:00–06:00). That leaves only aircraft in the QC/2-and-below tiers as candidates for night movements.
The practical effect is a fleet filter: the Boeing 747-400, a QC/4 type, simply cannot operate in that window. The same applies to older 767s if they are measured as QC/4. Meanwhile, a 787 or A350 — typically certificated at QC/2 or lower in most configurations — can go. The only exceptions are light propeller aircraft under 8,618 kg used for essential safety checks, and aircraft quieter than QC/0.125, which per CAA slip below the noise quota entirely — though they still count toward movement limits.
| Aircraft type (widebody long-haul) | Typical QC classification band (arrival/departure) | Eligible to operate in 22:30–05:00 night quota period? |
|---|---|---|
| Airbus A350 (new-generation widebody) | Classed within new-generation widebody group; QC bands at or below QC/2 for most certificated configurations | Yes; may operate if movement’s QC value is QC/2 or lower and noise quota allows |
| Boeing 787 (new-generation widebody) | New-generation widebody; QC bands at or below QC/2 for most configs, operational levels match classifications | Yes; may operate if QC rating is QC/2 or lower and quota available |
| Airbus A380 | New-generation widebody category; specific QC band depends on certificated EPNdB levels | Only if particular configuration is QC/2 or lower; QC/4+ banned in night quota period |
| Boeing 777 (classic widebody) | QC classifications from ICAO data; many variants QC/2 or QC/4 depending on engine/weight | QC/2 variants may operate; QC/4 variants banned in 22:30–05:00 window |
| Airbus A340-300 | QC/2 classification; operational departure noise often exceeds band | Qualifies as QC/2, but any configuration at QC/4 would be barred 22:30–05:00 |
| Boeing 747-400 | QC/4 classification; operational departure noise exceeds band | No; QC/4 aircraft prohibited in night quota period |
| Boeing 767-300 | Operational arrival noise lies above assigned QC band; potential under-classification | Only if QC/2 or lower; reclassification as QC/4 would ban it from quota period |
| Source: UK Civil Aviation Authority (CAA); NATS (UK air navigation service provider) | ||
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The voluntary layer on top of regulation
Heathrow’s published timetable says no scheduled departures from 22:40 to 06:00 and no scheduled arrivals from 22:55 to 05:05. On paper, that reads like silence. But the timetable reflects scheduling practice, not a legal wall. A voluntary arrangement — the Quiet Night Charter — asks airlines to avoid landing before 04:30. Delayed aircraft and specially approved flights still cross the threshold in the early hours. The result: the 04:30–06:00 stretch behaves like the real arrivals block, not empty airspace. A 787 running late from Singapore can still touch down at 05:00. A 747-400 cannot, no matter how late it is.
When the banding system can’t tell quiet from quieter
The scale that sorts aircraft into QC bands isn’t always precise in the real world. The CAA’s validation study monitored operational noise for 111 aircraft types at Heathrow and found that 13 of them produce approach noise entirely above their assigned QC bands. A340-300s, classified as QC/2, often exceed that band on departure. B747-400s, rated QC/4, do the same. B757-200s, B757-300s, and B767-300s sit entirely above their bands on approach — gaps the study says normal operational factors cannot explain.
The result is a scale that doesn’t always reward the quietest new jets or single out the loudest old ones. As CAA data shows, the broad bandings can let some noisier legacy types slip through while sometimes underestimating the actual noise of others.
Why a 3-decibel rule decides who flies
The Quota Count scale is built on a single physical fact: a 3-decibel increase in aircraft noise doubles the acoustic energy hitting the ground. That’s not a regulatory preference — it’s how sound works. So the scale doesn’t just add numbers, it compounds. QC/1 is twice as heavy acoustically as QC/0.5. QC/2 doubles again. QC/4 doubles again. By the time you reach QC/16, one movement spends the same noise budget as 64 separate QC/0.25 movements. This is why Heathrow’s 1993 shift from counting movements to counting noise was a fundamental change. A movement cap treats every aircraft equally. A noise budget makes the airline’s fleet choice the real variable. Airlines that bought new-generation engines before the rule tightened found themselves holding a structural advantage: their aircraft could fly at night while older types lost the privilege.
What the QC system means for travelers
None of this lives in the fare rules. But it decides whether a traveler from New York can book a 22:30 arrival at Heathrow or whether a Frankfurt-bound business traveler gets a 06:00 departure. Airlines that fly A350s and 787s can offer those slots. Operators still running 747-400s, older 767s, or A340s cannot — at least not between 22:30 and 05:00. For frequent flyers, this is a quiet filter on schedule quality. An airline’s night network at Heathrow is less about marketing strategy and more about whether its fleet clears the QC/2 bar. If a route lacks a night option, check the aircraft type. The restriction often explains why. And the 04:30–06:00 window remains the real arrivals stretch — not because airlines schedule there, but because late-running aircraft legally can.
Questions? Answers.
How much more noise quota does a QC/16 aircraft consume than a QC/0.25 aircraft?
One QC/16 movement consumes the same noise quota as 64 QC/0.25 movements. The QC scale doubles at every 3-decibel step: QC/1 is twice QC/0.5, QC/2 is twice QC/1, and so on up to QC/16.
Which aircraft are banned from operating in Heathrow’s night quota period, and which can still be scheduled?
Aircraft rated QC/4 or higher are banned during the night quota period (22:30–05:00). QC/8 and QC/16 are barred for the entire night period (22:00–06:00). Only aircraft at QC/2 or lower may operate in the night quota period, subject to the seasonal noise quota and movement limits.
Are any aircraft exempt from the QC noise quotas at Heathrow?
Light propeller-driven aircraft with a maximum certificated take-off weight up to 8,618 kg used for essential airport safety checks are exempt. Aircraft quieter than QC/0.125 are also exempt from noise quotas, but still count toward movement limits.
Why do flights still land in the 04:30–06:00 window if Heathrow has a night ban?
Heathrow has no scheduled arrivals between 22:55 and 05:05, but a voluntary agreement asks airlines not to land before 04:30. Delayed and specially approved flights may still arrive in the early hours. The 04:30–06:00 window operates as the practical arrivals stretch, not silent airspace.
