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Arrival rate and delay calculator
What spacing on final means for the runway, and how to absorb the delay when traffic beats it.
Landings per hour
Delay from slowing down
How much time a slower speed absorbs over a distance, without holding.
When traffic beats the runway
How big the queue gets while more aircraft arrive than can land.
The sums
- Landings per hour = groundspeed ÷ spacing
- Delay = distance ÷ slower speed − distance ÷ normal speed
- Queue = (arrivals − runway’s rate) × hours, and the last to join waits queue ÷ rate
At 140 kt, a 5 NM gap means 28 landings an hour, one every 2 minutes 9 seconds. Tighten it to 3 NM and the most you can get rises to about 47.
Why the headwind matters
What fills a runway is time, not distance. With a strong headwind on final, groundspeed drops, so the same 5 NM gap takes longer to fly and fewer aircraft land each hour. That’s why a windy day can cause delays even in clear weather.
Why real rates are lower
This is the most the spacing allows. Real rates are lower because each aircraft has to clear the runway before the next lands, wake turbulence calls for bigger gaps behind heavier aircraft, and a runway that’s also used for departures needs gaps for those. Controllers also leave a margin, since a go-around uses up a slot. Published airport rates are the ones to go by for any real airport.
Slowing down or holding
Slowing an aircraft well before the airport absorbs delay while it keeps moving towards its destination, and that uses less fuel than circling in a hold. It only goes so far, because an aircraft can only slow down so much and each one takes time to feel the effect.
Quick answers
How many aircraft can land per hour on one runway?
At 3 NM spacing and 140 kt, the spacing alone allows about 47. Real single runways achieve less, because of runway occupancy, wake gaps and any departures that share the runway.
How do you work out the time between landings?
Divide the spacing by the groundspeed, then multiply by 3,600 for seconds. 5 NM at 140 kt is 5 ÷ 140 × 3,600, about 129 seconds.
How much delay does slowing down absorb?
Over 100 NM, slowing from 300 kt to 250 kt absorbs 4 minutes: 24 minutes instead of 20.
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For training and simulation only. These calculators are for learning and for games. Their results are automatic, and they don’t account for everything a real operation does. Never use them for real flight planning, navigation or air traffic control. Use your official charts, approved tools and procedures.
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