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Why do some flights take longer than others to same destination on same day?

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Satsuma
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Why do some flights take longer than others to same destination on same day?

#30632

Postby Satsuma » February 11th, 2017, 3:03 pm

I am taking a long haul flight soon.

The airline offers two flights a day on the same aircraft to/from the same airports, yet the night flight is specifically listed as being 10 minutes quicker. On such long flights 10 mins is neither here nor there I know, but I am curious DAK why the 10pm flight is quicker?

Flight 1: Departs 10am, duration 13hours
Flight 2: Departs 10pm, duration 12hrs 50m

(Interestingly, there is a similar 20min discrepancy on the return flight.)


TIA
Sats

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Re: Why do some flights take longer than others to same destination on same day?

#30643

Postby melonfool » February 11th, 2017, 3:45 pm

Probably landing slots at the destination and how long they have to circle for before landing.

Or it could be headwinds at the time of day.

Mel

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Re: Why do some flights take longer than others to same destination on same day?

#30646

Postby NomoneyNohoney » February 11th, 2017, 3:54 pm

Yes, I too reckon it could be prevailing winds, depending what direction you're going. One way helps, one way hinders.

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Re: Why do some flights take longer than others to same destination on same day?

#30659

Postby gryffron » February 11th, 2017, 4:40 pm

Whilst I accept wind will affect flight time, I'd have thought they're unlikely to be able to predict wind for the same route, more than a few days in advance. Yes for different directions, but not for individual flights. So it is unlikely to be written into the schedules.

I'd say the likely reasons for a scheduled difference are
1) airports busier at certain times of day so more queueing to takeoff/land/taxi.
2) a different type of aircraft scheduled to operate the flight. They don't all fly at the same speed.

Gryff

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Re: Why do some flights take longer than others to same destination on same day?

#30669

Postby Lootman » February 11th, 2017, 5:26 pm

gryffron wrote:a different type of aircraft scheduled to operate the flight. They don't all fly at the same speed.

Yes, I found this list of mach numbers for the most common civil aircraft types:

Boeing 747-400 0.86
Boeing 787 0.85
Boeing 777 0.84
Boeing 767 0.80
Boeing 757 0.80
Boeing 737 -800 0.78
Boeing 737 - 300/400/500 0.74

Airbus 380 0.85
Airbus 340 -300/600 0.82
Airbus 330 0.82
Airbus 320 0.78
Airbus 310 0.78

http://www.askcaptainlim.com/flying-the ... iners.html

Four-engined planes are slightly faster than two-engined planes. Cruising speed also depends on altitude.

Another reason might be that night flights get routed a longer way in and out of airports due to noise abatement factors.

Estimated load factors might also affect routing, altitude and cruising speed.

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Re: Why do some flights take longer than others to same destination on same day?

#30681

Postby melonfool » February 11th, 2017, 6:25 pm

The OP says it's the same plane.

Mel

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Re: Why do some flights take longer than others to same destination on same day?

#30686

Postby Lootman » February 11th, 2017, 6:35 pm

melonfool wrote:The OP says it's the same plane.

There are various sub-types of most aircraft that have different characteristics. Take the 777 for instance. From Wikipedia:

"The 777 is produced in two fuselage lengths as of 2017. The original 777-200 variant entered commercial service in 1995, followed by the extended-range 777-200ER in 1997. The stretched 777-300, which is 33.25 ft (10.1 m) longer, followed in 1998. The initial 777-200, -200ER and -300 versions are equipped with General Electric GE90, Pratt & Whitney PW4000, or Rolls-Royce Trent 800 engines. The extended-range 777-300ER and ultra long-range 777-200LR variants entered service in 2004 and 2006 respectively, while the 777F, a freighter version, debuted in February 2009; these variants all feature high-output GE90 engines and extended raked wingtips. The 777-200LR is the world's longest-range airliner, able to fly more than halfway around the globe, and holds the record for the longest distance flown non-stop by a commercial aircraft"

Even with the exact same aircraft type and sub-model, there is often a choice of engine with different thrust ratings, as the citation indicates.

Another factor I didn't mention is that airports typically vary the flight paths at different times of the day, to avoid subjecting the same area and residents to noise all day long. So every 4 hours or so they may switch flightpaths and runways, which can alter flight times by varying amounts.

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Re: Why do some flights take longer than others to same destination on same day?

#30713

Postby Satsuma » February 11th, 2017, 8:46 pm

Thanks.

My bet goes on the minor last few miles re-rerouting/runway direction suggestion. Standard alternations or other changes to the final approach flight path could easily add a few mins to the schedule.

It's definitely the same plane they basically shuttle a couple of identical A380s back and forth, landing, cleaning and restocking before it takes off again a few hours later (AMHIK!).

Sats

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Re: Why do some flights take longer than others to same destination on same day?

#31052

Postby Bminusrob » February 12th, 2017, 7:54 pm

As has been said, it could simply be to do with available landing slots. A bit like driving, if you drive slower, you take longer to get to your destination.

Some years ago, I spent quite a lot of time going back and forth to Japan. The flight home normally takes about ten hours. However because of the times airports operated, this usually meant that if I had to work in Tokyo on Friday, I would lose most of Saturday flying home. I found out that I could get home much earlier by taking an Air France flight to Paris, then a short flight from Paris to London. The Tokyo to Paris flight was more or less the last flight to leave Tokyo on Friday night, and one of the first to arrive in Paris on Saturday morning. In order to achieve this, the plane (a 747) just flew slowly, taking 15 hours for the flight, when at other times of day, it only took 10 hours.

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Re: Why do some flights take longer than others to same destination on same day?

#35795

Postby ElectricFeet » March 2nd, 2017, 8:06 pm

As an ex-pat, used to taking the same flights/routes over many years, I find the answer often is that they set the time for PR reasons. If the airline feels there is risk of being late on the route, they add an extra 10 minutes or so, in order to be able to say that the flight arrived early most times and was never late.

This also explains why a flight-share should have different times: one airline has a lower risk appetite / fear of statistics than the other one does.

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Re: Why do some flights take longer than others to same destination on same day?

#35968

Postby DiamondEcho » March 3rd, 2017, 2:19 pm

Lootman wrote:
melonfool wrote:The OP says it's the same plane.

There are various sub-types of most aircraft that have different characteristics. Take the 777 for instance. From Wikipedia:


They also have different seat configurations, premium vs economy, depending on the demographic of the expected passengers. Hence passenger numbers and hence weight/speed.

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Re: Why do some flights take longer than others to same destination on same day?

#35974

Postby melonfool » March 3rd, 2017, 2:38 pm

DiamondEcho wrote:
Lootman wrote:
melonfool wrote:The OP says it's the same plane.

There are various sub-types of most aircraft that have different characteristics. Take the 777 for instance. From Wikipedia:


They also have different seat configurations, premium vs economy, depending on the demographic of the expected passengers. Hence passenger numbers and hence weight/speed.


Planes do, indeed, even within models. But the OP has specified that it is *exactly the same plane*.

Do feel free to go on explaining though....

Mel

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Re: Why do some flights take longer than others to same destination on same day?

#35987

Postby Lootman » March 3rd, 2017, 3:19 pm

melonfool wrote:Planes do, indeed, even within models. But the OP has specified that it is *exactly the same plane*.

It depends on what the OP understands as being "exactly the same". Usually when you book flights, the aircraft type will be shown (and in fact it is one factor I take into account when choosing a flight because I am picky about such things). But that information doesn't usually go beyond the base make and model so the average person will just see, say, 777, rather than 777-200, 777-200LR, 777-200ER, 777-300 or 777-300ER. They won't see engine options, or whether it is an early or late model.

As noted earlier, each of those variants has differences in wing design, fuselage length, engine thrust ratings, payload, burn rate and so on which will make a difference to performance. Not a lot, in most cases, but on a 15 hour flights it can be enough to make a 10 or 20 minute difference.

Depends how nerdy you want to get but I find this site useful for such information and, also, a good guide to selecting the best seat:

https://www.seatguru.com/airlines/Briti ... 77_300.php

And of course there can be a switch of metal for operational reasons so to find the actual plane flying a route, I use this:

https://flightaware.com/live/flight/BAW285

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Re: Why do some flights take longer than others to same destination on same day?

#35999

Postby DiamondEcho » March 3rd, 2017, 3:47 pm

melonfool wrote:Planes do, indeed, even within models. But the OP has specified that it is *exactly the same plane*. Do feel free to go on explaining though.... Mel


Former point) No he didn't
And latter) No idea what you mean by that. But anyway that's not what he said which was [my bold]:

Satsuma wrote:The airline offers two flights a day on the same aircraft to/from the same airports

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Re: Why do some flights take longer than others to same destination on same day?

#36024

Postby melonfool » March 3rd, 2017, 5:19 pm

DiamondEcho wrote:
melonfool wrote:Planes do, indeed, even within models. But the OP has specified that it is *exactly the same plane*. Do feel free to go on explaining though.... Mel


Former point) No he didn't
And latter) No idea what you mean by that. But anyway that's not what he said which was [my bold]:

Satsuma wrote:The airline offers two flights a day on the same aircraft to/from the same airports


SHE also said "It's definitely the same plane they basically shuttle a couple of identical A380s back and forth, landing, cleaning and restocking before it takes off again a few hours later (AMHIK!)."

Mel

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Re: Why do some flights take longer than others to same destination on same day?

#36050

Postby Lootman » March 3rd, 2017, 7:10 pm

Satsuma wrote:The airline offers two flights a day on the same aircraft to/from the same airports

It's definitely the same plane they basically shuttle a couple of identical A380s back and forth, landing, cleaning and restocking before it takes off again a few hours later (AMHIK!)

OK, I'll ask, how do you know?

There is actually only one variant of the A380 at the moment - the A380-800. There is a choice of two engine types and there is an earlier and a later build version, but that's really not going to make a material difference to flight performance.

If you enter the flight numbers into the flightaware site I listed earlier, you can see a log of the actual flight times going back in time, and perhaps detect a pattern.


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