Same route, same aircraft, different block time
 

Is it common to have substantially different block times on the same route when the aircraft is the same as well?

I am looking at the EWR-YHZ-EWR route, operated with Expressjet's Embraer 145. Most days, there are two rotations.

EWR-YHZ flights always have a block time of 1:57h.
YHZ-EWR flights have either 2:07h (morning) or 2:33h (afternoon). Weekend or weekday, doesn't matter.

As you can see, the block time of the afternoon YHZ-EWR flight is about 1/3 longer than any EWR-YHZ flight. And that is not due to jetstream effect, as the morning flight is much faster. Yes, variations in traffic affect travel time, but wouldn't that be more a problem in the morning rush than in the afternoon, and wouldn't such variations affect both directions?

Generally, I wouldn't care about the block time. I have flown this route many times. But with the current time table, the longer afternoon block time pushes me out of the minimum connection time at EWR.

Yes, if not 'jetstream' then it's due to United 'blocking' additional time. All airlines pad their schedules and being an afternoon flight, United probably does this due to the fact that everything inherently takes longer in the afternoon. Taxi-way times will increase. Time from gate to takeoff will increase. Time from landing to gate will increase due to traffic/other aircraft / anything really.

Indeed. I've flown this route many times, sometimes in only 1:10h.

If that is the reason, why does the block time only increase Southbound but not Northbound? Any increase in taxi-time and holding patterns etc. would affect all afternoon flights, not only in one direction.

I haven't checked for EWR, but in YHZ there are more flights around the morning departure than around the afternoon departure.

Not necessarily. There could easily be a regular, known delay at a particular airport that affected departures but not arrivals.

Seems pretty normal and logical.

Time of day weather
Loads
Incoming aircraft
Gate issues at either end
Airport congestion
Overall flight congestion

Don't neglect the rotation of the earth.

Why?

This one does not need to deal with the vagaries of the jet stream. Think about air traffic flow and into YHZ and into EWR in the afternoon. Which one takes longer?

When was the last time you experienced an ATC hold over YHZ? How about in the NYC area?

depends on some of the more specifics. the specific times of the flights will have more or less congestion, depending on the amount of traffic in the area and on the ground at the scheduled time. I have no idea when the flights leave either direction, but very possible the YHZ-EWR afternoon flight lands at an extremely busy time, meaning they may be expecting to have a longer time of decent/approval on final, as well as greater taxi time when close to arrival time, whereas the afternoon departure from EWR may not be such a busy time.

Beyond that, there may be other items. For example, while taxi time may be as busy for both, once a departing flight actually leaves, it'll get out of the area quickly, while an arriving flight has to get in line for their actual landing, which could take time, them have the extra taxi time due to traffic on the ground. At YHZ, they generally aren't having those kinds of heavy traffic issyesvin the air or on the ground than NYC-area does.

#2 is not true, especially at jet stream levels.

If you look at a flight with heavy frequencies, like SFO-LAX, you'll see that UA blocks different times for that flight at different times of day, even for the same aircraft type flying in the same direction.

The bottom line here is that UA has all the historic data on how long particular flights take at particular times, and presumably it uses that data on an ongoing basis to set block times.

I've checked similar cross-border routes operated by ExpressJet with Emb 135/145: EWR-YQB-EWR and EWR-YUL-EWR. I don't see such large variations in block time there. Actually, in YUL, the mid-morning departure 10:37 am has a bit longer block time than the early morning and afternoon departures.

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The wind doesn't affect north-south routes as much, so the flight time is probably similar. EWR to YQB and YUL are almost due north and much shorter than it is to YHZ. United and others uses historical data to publish block times. The afternoon is almost always more congested at EWR, hence the longer block times. It all comes down to the algorithms they use.

I hear you, but that congestion is the same whatever direction you come from.

Sorry... it is not that simple.

Congestion and flight times are a result of many factors. Not just the direction of flight.

Though you answered about EWR afternoon congestion, there is also congestion from the originating flight, and the actual path that each plane will be assigned to fly. Unlike a railroad, ,planes usually do not fly the same path each time.

They block time based on many factors - with I would guess, a heavy emphasis on historical data.