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What about doubling the length of airfields in order to shorten the time it takes for a plane to roll on the ground after landing and before takeoff. The plane could take off from the middle of the air-lane and when it lands it can turn off in the middle, in order to minimise the driving time to and from the terminal. Why don't we see this and what does it take to achieve it?

I had expected a calculation as an answer to this question. Taxiing takes 23 minutes. In Sweden savings for private travel is evaluated to €4 per hour and $20 for business.

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    $\begingroup$ Smaller planes can already do this at larger airports, it is known as an intersection takeoff. And depending on where the destination is at the landing airport, we can turnoff the runway earlier once slowed down vs going all the way to the end of the runway. It all depends on the size/speed of the aircraft; a large jet needs more rolling time both for takeoff & landing with all that momentum vs a small 2/4/6 seater that can be airborne and landed/slowed down in well under 2000 ft. $\endgroup$
    – CrossRoads
    Nov 28, 2018 at 13:34
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    $\begingroup$ Or you could have two shorter runways side-by-side... Pretty sure that is very common throughout the world... $\endgroup$
    – Ron Beyer
    Nov 28, 2018 at 15:12
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    $\begingroup$ Cost is a good reason not to do this. Instead of having 2 9,000' parallel runways that are potentially useful simultaneously, you have 1 18,000' runway that you're only using half of. $\endgroup$
    – FreeMan
    Nov 28, 2018 at 18:41

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Not quite to the same extent you have in mind, but when you are able to have a staggered set of runways, they will try to arrange it so that the "landing" ones have the roll out area near the terminal, and the "takeoff" ones have the threshold near the terminal.

Let's take BWI as an example. In an south/east flow (takeoffs and landing heading south/east), all traffic will take off on 15R, right next to the NW end of the terminal. All traffic will land on 10, with the exit from the rollout a little bit after the runways cross.

Or IAD, in a North flow, most landings will happen on 1R and takeoffs on 1C.

NAS (naval air station) Lemoore is another sort of example of this - kind of a little split because of the structure of the ramp, but if it was one terminal, in a NW flow you'd have all takeoffs on the N runway and all landings on the S runway.

Put another way, if you have a 9000 foot runway, in your scheme you'd need to make 1 18000 foot runway, but it is at least twice as efficient to have 2x9000 ones, even if it increases the taxi time, and some of that can be mitigated by the staggering above.

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  • $\begingroup$ Not so at KATL. Land on the outboards, depart on the inboards (with a midfield terminal). $\endgroup$
    – RetiredATC
    Aug 12, 2023 at 20:18
  • $\begingroup$ @RetiredATC yes, it depends on geography and how the land is available. NAS Lemoore as in my example is "optimized" for this sort of flow, but ATL can go both ways (and LAX,DFW) $\endgroup$
    – Aaron
    Aug 29, 2023 at 22:23
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The cost is that it would required a runway twice as long.

Airports already take up enormous amounts of land. Designers try to build airports near major centers, so taking up twice as much valuable land for longer runways near a major population center is a huge cost.

The longer runways also need to be cleaned, maintained, and snow-plowed.

That is a lot of cost and difficulty just to reduce taxi-time by a couple minutes. After one has taken a 2 hour cross-country flight, 5 minutes of taxi-time is not a point of concern.

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    $\begingroup$ Denver International Airport was designed to minimize taxi times as well as allow for simultaneous parallel operations when necessary. The runways are laid out in a 'pinwheel' with one end near the terminal. With a northerly wind you can land on 35L and 35R and roll out near the terminal on the east. Takeoffs can use 34L and 34R which start near the terminal on the west side. In bad weather you can use 34L and 35R to get the separation for parallel ops though the 34L aircraft will have a longer taxi. $\endgroup$
    – Gerry
    Nov 28, 2018 at 13:39
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    $\begingroup$ Anyone who has landed at DIA may question that it minimizes taxi times. I've often heard it joked that planes land at the Kansas Border, and drive in to Denver. $\endgroup$
    – abelenky
    Nov 28, 2018 at 15:06
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    $\begingroup$ 5 minutes taxiing for 200 passenger compares to a cost of say USD 1300, regardless of how long time the flight takes. Is there a calculation somewhere about savings and costs? $\endgroup$
    – David Jonsson
    Nov 28, 2018 at 16:22
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    $\begingroup$ @abelenky i said it was designed to - I didn't say it was successful. But it does apply a concept very similar to what the question proposes. And taxi times at DEN are typically better than DFW. Flying between DFW and AUS, it wasn't unusual to have taxi times at DFW greater than the flight time. $\endgroup$
    – Gerry
    Nov 28, 2018 at 16:48
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    $\begingroup$ Cost? Concorde used 1200 kg of fuel just to taxi. $\endgroup$
    – David Jonsson
    Sep 26, 2020 at 10:29
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Notice that most airports are square-ish. For various reasons, it's usually a lot easier to get a compact parcel of land than a long, thin one. In particular, aviation authorities really don't like roads going under runways, so the airport as a whole creates problems for the highway system around it; double the length of the runways and those problems get much worse. In the old days, a square parcel was used to provide several (intersecting) runways at different angles, but many have been rebuilt to have parallel (and thus simultaneously usable) runways in the same compact area; taxi times might be a bit longer, but overall throughput is much, much higher.

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As pointed out by Crossroads. Smaller aircraft use only a small portion of the runway. Therefore, they can and do start their takeoff rolls at other points accessible from taxiways other that the end of the runway. These are called intersection departures.

Most large aircraft and many smaller aircraft will avoid or decline intersection departures. Large aircraft must have the distance to be able to accelerate to takeoff speed, immediately decelerate from takeoff speed, and come to a complete stop before the end of the runway. Smaller aircraft benefit from maximizing the full length of the runway in order to have enough distance for landing on the same runway in case of an engine-out scenario while climbing out during departure.

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In many cases, planes can already take off from the middle of a runway. Elongating the runway is not the issue. As an illustration, a runway that can accommodate a fully loaded 747 is at least 10000 feet. Many hub runways are over 13000 feet. The ATR-72 and E-175, both fairly common aircraft, need less than 5000 feet to take off.

You want to have aircraft park on the ramp in the middle of the runway and takeoff with minimal taxiing from the middle of the runway. The reason this is impossible is that the ramp does not fit at the middle of the runway.

Take a look at these two recent airport designs (Daxing and Noida). enter image description here enter image description here The terminal and ramp area is usually about 1/3 the length of the runway, and sometimes much more. At smaller airports, the terminal and ramps are smaller, but the runway is too. The ramp is still about 1/3 the length of the runway.

Since the ramp is so big, it makes more sense to add another runway at the other end of the ramp instead of making the existing runway longer. This is exactly how Daxing and Denver airports are designed.

enter image description here

The Denver airport layout is not widely copied because most airports are built in places where land is more expensive.

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  • $\begingroup$ Can you show a cost comparison between land and taxi time? $\endgroup$
    – David Jonsson
    Nov 26, 2023 at 22:51

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