Spectators Balcony (Spotters Corner)If you're not a professional pilot but want to discuss issues about the job, this is the best place to loiter. You won't be moved on by 'security' and there'll be plenty of experts to answer any questions.
1) Why would an airline allot different flight durations for an outbound and return flight? Route in question is STN-BDS. 07:55-11:45 (2 hours 50) outbound and 12:10-14:15 (3 hours 5) inbound? The scheduling department cannot know the exact flight's duration in advance and I know there is always a 'buffer', but why the extra fifteen minutes on the return flight?
2) Is there a website that gives accurate, actual flight durations? I know FR don't put details on FlightStats, but are there any others?
Another reason for longer published times is the destination. If you are going into LHR, then you have to allow holding time and taxi time. If you are going into, say, Southampton, then times are shorter. This applies to many destinations.
Lastly, as you may well know, airlines now always quote the longest possible block time and a scheduled departure time that is well in advance of their slot time. This helps to get us on board and away - as well as any routing and weather delays - to ensure that the they can mark more on time arrivals.
Nicholas, you can't really have "accurate" flight durations. They very much depend on route taken on the day and the winds. On an Atlantic crossing for example flight times can differ by anything up to half an hour westbound and an hour eastbound.
This information will be collected by and available to those who need it - the airline involved and Eurocontrol CFMU, for example.
An airline will typically monitor every flight duration for each individual flight number. This will enable them to create a frequency distribution which will be pretty much a normal bell-shaped curve. They can then apply this to their own in-house policy to determine scheduled flight times. For example, they may aim to publish a scheduled block time which has been achieved on 85% of occasions in the latest schedule period. In this way block times may be adjusted over time.
How long is a piece of string? Simply measure the distance and divide it by about 400kts and you won't be far off. Problem is that every day, every hour, every minute is different in such a dynamic situation. Wind makes a heck of a difference and air traffic delays can pop up anywhere, any time. A flight that gets a straight-in one day might be held for 40 minutes the next..
Somebody asked what "time" is recorded for stack-leaving. It's the actual time the aircraft passes the beacon to commence approach. EATs are calculated on those times but what other agencies do with the info I do not know.
If you look at flight tracking websites you can often find groundspeed. Compare that for a selection of westbound and eastbound flights. You will soon get an idea why westbound flights take longer.
Incidently Cathay put a lot of detail on Flightstats (perhaps too much, including several changes in estimated arrival time) but you can get a lot of useful information.
It is interesting to look at old timetables and see how the timetabled block time has changed throughout the years. It has increased significantly for short haul flights to and from Heathrow over the last twenty years owing to longer taxi times and more time in the stack. The number of movements at LHR has increased significantly over the period but at a cost - ATC will land several widebodies followed by several narrow bodies which increased capacity owing the increased separation required when the later follows the former.
There are instances where an airline will timetable different block times on different days of the week owing to different routings - it may fly over certain countries in order to retain overflying rights. (Have a look at EK 125 from DXB - VIE which is 35 minutes quicker on Thursday.)
I booked a flight between JFK & DCA a few years ago (DL 3115 operated by Mesaba) which was timetabled to take 1 hr 55 mins. It covered the 215 miles in about a third of this time. However you can often be delayed out of JFK and when I checked the statistics the flight reported very good punctuality!
I'm am definately not an expert on overflying rights - probably more info on the Flight/Ground Handling Forum. However I know that the former Soviet Union and presumably now Russia charged a significant fee for overflying their territory. It could be that EK are quicker on Thursdays as the pay Russia for overflight rights. If they did not overfly the country the agreement might lapse after a while. There could also be limits in a bilateral agreement.
There was a time with BA / BCal used to fly nonstop twice a week from London - Tokyo & have to stop once a week at Moscow. Flight times between HKG & London used to vary as routings had to vary owing to limited overflying rights. (The block time from HKG - LHR could be as high as 14 hr 40 mins.)
As I say I am not an expert on this, perhaps an expert out there might be able to give a bit more detail.