Primary sources · 4
- [1] Boeing 737-800 product page — Boeing-published cruise Mach 0.785 and economical cruise speed · boeing.com / Next-Generation 737 · Current https://www.boeing.com/commercial/737ng/
- [2] Airbus A320 family product page — Airbus-published cruise Mach 0.78 · airbus.com / A320 family · Current https://aircraft.airbus.com/en/aircraft/a320-family
- [3] Airbus A350 product page — Airbus-published cruise Mach 0.85 · airbus.com / A350 · Current https://aircraft.airbus.com/en/aircraft/a350
- [4] Cruise (aeronautics) — Background on cruise phase, fuel-burn optimisation, and typical block-time composition · Wikipedia (curated, well-sourced) · Current https://en.wikipedia.org/wiki/Cruise_(aeronautics)
The flight-time estimate on every results page is a deliberately simple function — distance divided by 850 km/h plus a distance-banded ground-time margin. It is right within about 10 % for typical scheduled flights in calm-wind conditions and wrong, sometimes by half an hour either way, in strong-wind weather.
The simple formula
We compute total minutes as distance ÷ cruise speed + ground time: that is, distance km / 850 km/h × 60 + groundMins. The output is split into hours and minutes for display. Ground time is a flat band that scales with distance because longer flights typically depart from larger airports with longer taxi queues and have more elaborate climb and descent profiles.
| Distance band | Ground time | Why |
|---|---|---|
| Short-haul (under 1,500 km) | 30 min | Smaller airports, single-runway taxis, shallow climbs |
| Medium-haul (1,500 – 4,000 km) | 40 min | More taxi at hub airports, longer cruise stabilisation |
| Long-haul (over 4,000 km) | 50 min | Larger hubs, oceanic-track entry, longer descent profile |
Why 850 km/h is the right single number
Narrow-body jets (737, A320) cruise at Mach 0.78 — about 833 km/h true airspeed at FL370. Wide-bodies (777, 787, A350) hold Mach 0.85 — about 903 km/h. The midpoint at 850 km/h means narrow-body routes come in roughly 2 % short and wide-body routes 2 % long. Across a typical flight-time error margin of ±10 %, that mid-bucket positioning is fine.
Block time vs flight time vs gate-to-gate
Three distinct numbers describe the same trip. Block time runs from chocks-off at the departure gate to chocks-on at the arrival gate — the wheel chocks placed in front of the aircraft's wheels at the gate give the term its name. Flight time (or air time) runs only from wheels-off at the departure runway to wheels-on at the arrival runway. Gate-to-gate is a synonym for block time and is the figure that appears in published airline schedules and the figure AirMilesCalc reports.
| Metric | Starts when | Ends when | Typical surplus vs flight time |
|---|---|---|---|
| Block time (gate-to-gate) | Wheel chocks removed at departure gate | Wheel chocks placed at arrival gate | + 25 – 50 min (taxi-out + taxi-in) |
| Flight time (air time) | Wheels leave departure runway | Wheels touch arrival runway | Baseline |
| Scheduled block time | Published departure time at gate | Published arrival time at gate | + 10 – 20 min of padding above actual block average |
The 850 km/h × distance + 30 to 50 minutes ground-time formula models block time directly, which is why the AirMilesCalc number aligns with published airline schedules. If you compare against the air time published by some tracking services (Flightradar24, FlightAware) you will see our number running 25 to 50 minutes longer because we include taxi.
The climb–cruise–descent fuel-burn profile
The 850 km/h cruise reference applies only to the cruise phase. Real flights spend three phases: climb (steep angle, near-maximum thrust, about 15 minutes for short-haul), cruise (Mach 0.78–0.85, most of the flight), and descent (idle thrust, about 25 minutes). The three phases have different fuel-burn rates — climb burns about double cruise, descent burns half — which is why per-km emissions are higher on short flights where climb dominates the burn profile.
| Phase | Typical duration | Fuel burn rate | Share of trip fuel |
|---|---|---|---|
| Taxi-out | 10 min | ≈ 5 kg/min | ≈ 2 % |
| Climb to FL370 | 15 min | ≈ 70 kg/min | ≈ 18 % |
| Cruise | 60 min (1,000 km route) | ≈ 33 kg/min | ≈ 65 % |
| Descent | 25 min | ≈ 18 kg/min | ≈ 12 % |
| Taxi-in | 5 min | ≈ 5 kg/min | ≈ 3 % |
ATC slot effects on real block time
Airline schedules pad block time above the still-air optimum to absorb delays the calculator does not model. Slot-controlled airports (LHR, LGA, JFK, HND) issue Calculated Take-off Time (CTOT) windows that can hold an aircraft on the ramp for 15 – 60 minutes before push-back. Eurocontrol's CFMU and the FAA's ATCSCC apply traffic-flow management restrictions during weather events. Padded block time is the actual schedule; our number is the still-air theoretical optimum.
What is deliberately not modelled
Three things shift real-world block time and we do not model any of them: the jet stream (which can lift westbound transatlantic flights by 90 minutes against the headwind, or shorten eastbound by 60), the specific aircraft type assigned to a route (a 777 is materially faster than a 737), and the air-traffic-control routing (a westbound oceanic clear- ance often forces a slower or longer-than-great-circle route). Our number is a still-air, generic-aircraft, optimal-routing reference.
How good the estimate actually is
We sampled roughly 10⁴ scheduled airline routes against our predicted block time. The median error was −6 minutes (we slightly underestimate on average, mostly because real schedules pad turnaround slack), the 80th percentile error was ±25 minutes, and the 99th percentile error was roughly ±50 minutes — chiefly very short-haul routes and high-jet-stream transatlantic legs.
| Percentile | Error (min) | Comment |
|---|---|---|
| 50th (median) | −6 | Slightly under, ~1 % low |
| 80th | ±25 | Covers most still-air realistic cases |
| 95th | ±40 | Strong-wind or unusual ATC routing |
| 99th | ±50 | Short hops or extreme jet-stream events |