Same Route, Same Plane, Same Day, Different Flight Times?
 

On SNA->SFO today, there are six flights, four on E175s. The scheduled flight times for those identical flights are 1:27, 1:28, 1:29, and 1:34. How are those scheduled flight times decided, and why would they be different?

Just to mess with your mind, obviously :p

Anticipated/historical congestion at departure or arrival airports?

(Kind of) interesting to me is whether if on different days of the week, the same flight's anticipated flight time varies, do they break those out into different lines of the schedule (you know the old PDF schedule)?

Extrapolation of historical data, including expected traffic delays, anticipated routing, winds aloft, planned fuel loads, and probably a lot more.

Where are you seeing this -- looking at flight status @ mobile.united.com -- this is reported
And actual departures seem close to scheduled times.

Which corresponds exactly to the flight durations in the OP for the E-175 flights.

UA5337 duration 1:34 (11:23 - 12:57)
UA5933 duration 1:28 (3:05 - 4:33)
UA5791 duration 1:27 (6:15 - 7:42)
UA5873 duration 1:29 (8:20 - 9:49)

Ahhh -- flight times as in length of flight, not flight times as in departure and arrival times. Guess I'm being a bit dense today :D

Got lock on a similiar recent thread - http://www.flyertalk.com/forum/unite...ariations.html

I'm a scientist, so it definitely captured my attention!

What I will perhaps never understand is that it's all fake precision. You can estimate one flight to be two minutes longer an average because of more taxiing delays at SFO, but departure (push) time variance is going to dwarf this computation so I really wonder.. what value can it possibly provide?

Seems weird to extraploate to that fine scale of single minutes, when completely unpredictable, yet ubiquitous, factors introduce much larger variation in flight duration.

They have to pick something.

And if there are known and repeatable variations in performance at different times of day (and, yes, there absolutely are; I've run the numbers on DOT data covering a large span of time and documented it for another job) then you absolutely should account for it in planning. Moreover, more aggressive scheduling means generally lower labor costs, assuming the schedule can hold. The airline's goal has to be to schedule the bare minimum it can reliably operate. And UA's on-time numbers keep ticking up.