remcor
Posts: 307
Joined: Thu Feb 16, 2006 9:25 am

### Ideal Long-haul Leg Length?

Is there an ideal distance/time between two cities for airlines such that they can do daily flights with the fewest amount of aircraft, and does this affect fares?

For example:

If cities A and B are, say, 10 hours apart, then a single aircraft could fly from A to B, turn around and fly back from B to A and be ready to do it all over again the next day.

However if cities A and B are 11.5 hours apart, then you couldn't turn around and fly that aircraft back to city A in time to make the next daily flight.

So in theory, shouldn't there be an ideal flight time between two cities such that daily flights are possible with 1 aircraft? And if a city is only slightly farther away, shouldn't it mean a dramatically large fare increase for that extra distance?

[Edited 2007-03-21 17:31:48]

DiscoverCSG
Posts: 566
Joined: Wed Jan 31, 2007 2:22 am

### RE: Ideal Long-haul Leg Length?

 Quoting Remcor (Thread starter):So in theory, shouldn't there be an ideal flight time between two cities such that daily flights are possible with 1 aircraft?

Well, sort of. As you suggest, a rotation is most efficient if both legs fit in a 24-hour period with a moderate turn time.

In practice, though, consider these:

1. Block time is rarely the same in both directions. The main factor here is wind - eastbound flights over the North Atlantic have a tailwind, while westbounds have a headwind. This means the eastbound leg is shorter than the westbound leg.

Another factor is congestion. For example, EWR is known, at certain times of the day, for having long lines for departure - 45 minutes there isn't unusual in morning and evening rushes. Since this is a regular part of flying the route, it must be figured into the block time. Also, some airports experience holding for arrival (either in the air or via ground delays) - LHR, ORD, and the like come to mind, so this must also be added into the block time. A flight EWR-LHR, then, must allow for both departure queues and arrival holding. The return, on the other hand, might involve less taxi out time and less holding on arrival.

 Quoting Remcor (Thread starter):And if a city is only slightly farther away, shouldn't it mean a dramatically large fare increase for that extra distance?

No. Airlines (usually) don't use the same aircraft to run the same route every day. For example, CO runs 772's on both EWR-CDG-EWR and IAH-CDG-IAH. The EWR roundtrip takes somewhat less than 24 hours including ground time; the IAH roundtrip takes over 24 hours. By routing the 772 EWR-CDG-IAH-CDG-EWR (for example), CO uses two 772's to cover two routes over two days - thus bringing fleet utilization back to 1 bird per route.

The other part of the answer to this question is economics. Prices are set as low as they need to be set for people to be willing to buy them - often, this means matching a competitor's fare. If prices were set lower than this, airlines would be losing revenue because people are willing to pay more. If prices were set higher, passengers would buy a competitors' ticket, thus also causing the airline to lose revenue. If airlines could sell tickets based on what it cost to transport people, I'm sure they would. If this were the case, maybe we wouldn't be seeing so many companies in bankruptcy (e.g. DL and NW) or being sold (SN, TW).

remcor
Posts: 307
Joined: Thu Feb 16, 2006 9:25 am

### RE: Ideal Long-haul Leg Length?

Interesting comments, thanks. The routing example you provided really makes sense.

It is interesting to think how complicated airline routing must be, considering all the various factors to try to make a system that is marketable, reliable and economical.

It's interesting to think then how a slight increase in aircraft speed, say from Mach 0.81 to Mach 0.85, might have a significant impact on the airlines overall routing system.

DiscoverCSG
Posts: 566
Joined: Wed Jan 31, 2007 2:22 am

### RE: Ideal Long-haul Leg Length?

 Quoting Remcor (Reply 2):It's interesting to think then how a slight increase in aircraft speed, say from Mach 0.81 to Mach 0.85, might have a significant impact on the airlines overall routing system.

Efficiency in routing is one thing. On the other hand, scheduling planes with minimal turn times isn't a good idea, either. While some delays are normal and built into the schedule, things like snowstorms, strikes in foreign countries, and exploding engines are not normal (all have happened to CO in the last few days), and the schedule needs to have some slack if normal operations are to be recovered.

While some turns are done in the 90-minutes (minimum) that a widebody needs, others are longer, so that there's time to recover from delays.

Thus, changes in cruise speed (as when a 767 is subbed for a 777), aren't likely to have such a terrible impact.

As you can tell, I'm fascinated by routing, particularly of longhaul planes - it seems you are, too!

Evan767
Posts: 2198
Joined: Wed Aug 24, 2005 10:52 am

### RE: Ideal Long-haul Leg Length?

Yeah this is what DL does. You'll notice they fly the routes to Eastern Europe from JFK mainly, not out of the ATL megahub. The reason being is for better ground time for their 763's. Ex. If DL went ATL-KBP-ATL, ground time would be very short and difficult to service the 763, enplane/deplane passengers, etc. This is a main reason they start these routes from JFK.
The proper term is "on final" not "on finals" bud...

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