CoolGuy
Topic Author
Posts: 366
Joined: Tue Jan 18, 2005 8:13 am

Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 4:53 pm

For example, one flight EWR-CLE can take 1:44, but another at a different (busier, probably) time, takes 1:59

Also, LGA-ORD may take 2:30, but the reverse is 1:56.

Does traffic really affect the scheduled times that much?
 
lamedianaranja
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 5:14 pm

It depends on taxi-times too. AMS-LHR takes 1.30 hours in the timetable but actual flying time is almost never more than 50 minutes. As it's such a busy route the airline prefers to take that into account right away and not always arrive 'late'.

The difference in returns may also be caused by prevailing wind directions.
I wish that all skies were orange and blue!!
 
SonOfACaptain
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 5:22 pm

They want to screw with your mind.  angel 

Seriously though, there are many factors that effect the "flight time" of a flight. Commercial flying isn't as simple as flying directly to your destinations. You have to take account of traffic (both in the air and on ground), taxi time, and many, many other factors.

-SOAC
Non Illegitimi Carborundum
 
ehho
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 5:34 pm

It depends very much on the air corridors the flight gets assigned. When I flew PEK-AMS and AMS-PEK earlier this year, on the way there we took a southern route flying over Moscow and Omsk, while on the way back it was over Surgut and St. Petersburg, hundreds of miles to the north.

Check these recent QF LAX-JFK-LAX flights. On some days the fly over Missouri, on others near the state line between the Dakota's. Big difference:

Flightaware QF108
"Get your facts first. Then you may distort them as much as you please" -- Mark Twain
 
HT
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 6:04 pm

Quoting CoolGuy (Thread starter):

For such short flights as mentioned in your original post, like LAMEDIANARANJA pointed out taxi times ( = waiting in queues ) can be major factor if busy airports are involved.

For longhaul flights (especially East <-> West) , the difference between haed and tail winds make the difference. These presisting winds (aka. Jetstreams) also have an influance on the exact routing.
Flights from Europe to the U.S.-West coast usually fly much further north than on the return: This way they make the best out of trying to avoid head winds (fyling west) and making use of tail wind (flying east).
-HT
Carpe diem ! Life is too short to waste your time ! Keep in mind, that today is the first day of the rest of your life !
 
Tristarsteve
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 6:53 pm

Also the winds on the day can make a huge differencr.
LHR-ARN takes about 2hr 10mins.
But I have seen flight times of 1hr 50mins up to 2hr 45mins, just because of the wind.
 
flyingfool
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 11:40 pm

For excample, I've travelled RTM-DUB and EIN-DUB, RTM-DUB took 1:50 minutes and EIN-DUB (which is a longer flight in distance) took only about 1:15 minutes on almost the same routing...
This has all to do with strong headwinds.

Regards, Flyingfool
 
BMIFlyer
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 11:42 pm

Taxi times
Prevailing winds
Aircraft type
Traffic Patterns
Weather

You name it, it all happens, and can affect flight times in big ways  Smile



Lee
Sometimes You Can't Make It On Your Own
 
bistro1200
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RE: Why Do Flight Times Vary So Much?

Sun Nov 05, 2006 11:56 pm

From what I've heard, airlines typically use 55-65% reliability in their block times. This means that of 100 flights, 55-65 of them arrive at or under the published block time. Northwest I heard went to 50% block times, where half of all flights are automatically late. This was to save pilot costs.

It's a toss-up though, since lowering the block time makes for less crew costs (most crews are paid either the scheduled hours or flown hours, whichever is greater) while hurting on-time reliability and likely missed connections. Raising the block time makes for better on-time at the expense of crew costs and connections.

Don't forget connections in this equation. Say you are flying LAX-JFK-Europe, and your connection is planned right at the minimum connection time, say 45 minutes. If your airline uses 50% reliability, then you have a 50% chance of being late for your European departure at JFK, even if you leave LAX on time. Raising that to 65% means raising the block time, but now your connection time is only 38 minutes (example), so your routing is no longer legal. Retiming the LAXJFK flight might work, but now you may miss the inbound traffic from HNL or SAN. Cutting the minimum connection time is also something you don't want to do (especially to International flights) since that will cause in increase in DB's and general bad feelings by the passengers that missed it.

This is the stuff that airline managers have to figure out regularly.
Measure to the millimeter, mark with a crayon, cut with an axe.
 
cs03
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RE: Why Do Flight Times Vary So Much?

Mon Nov 06, 2006 12:18 am

All the above replies are correct for why airlines "pad" the schedule.
 
ckfred
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RE: Why Do Flight Times Vary So Much?

Mon Nov 06, 2006 9:47 am

I haven't looked in a while, but AA flights on ATL-ORD used to have an extra 10 to 15 minutes during the evening rush hour, because those flights almost always got stuck in a long line of departures waiting for takeoff at ATL.

Quoting EHHO (Reply 3):
It depends very much on the air corridors the flight gets assigned. When I flew PEK-AMS and AMS-PEK earlier this year, on the way there we took a southern route flying over Moscow and Omsk, while on the way back it was over Surgut and St. Petersburg, hundreds of miles to the north.

Even on shorter routes, there can be a difference. On ORD-ATL, the southbound flights generally fly from ORD to Danville, IL, then to Nashville, TN, then enter into the ATL pattern from the west.

Northbound, planes generally depart on a north-northwest heading, going to Chattanooga, TN, Louisville, KY, Indianapolis, IN, then entering the ORD pattern from over Lake Michigan.

The southbound flight usually runs 5 to 10 minutes shorter, because it's closer to being a straight flight path than the northbound routing.