gglave

My office just booked me on a trip on UA from YVR to LGA via ORD. This was the first time I noticed the one-time performance listed in the itinerary - One homebound leg is listed as on time "30% of the time", the other one "50% of the time"

If you have enough data that you can calculate your flight is delayed 70% of the time, why wouldn't you adjust the schedule for that flight? i.e. if it arrives 45 minutes late 70% of the time, why wouldn't you adjust the arrival time in the schedule so the flight returns to 'on-time' performance? Ditto with the flight that's late 50% of the time?

Seems odd to me.

Cheers,
Geoff Glave
Vancouver, canada

Carioca Canuck

You've probably got no more than 45 minutes between connections as well !!! LOL !!!

I find ORD and SFO to be the worst % wise.

tjl

ORD's capacity gets reduced in bad weather (which is often). But its flight schedule uses up its fair weather capacity. UA, AA, and the airport probably don't want to reduce flights for various reasons, so any flight involving ORD is going to be risky for weather delays.

Be prepared to be stranded at ORD when you miss your connection. Sign up for Hilton HHonors because there is a Hilton at the airport.

SixAlpha

The folks at ORD have, theoretically, been working actively to reduce congestion at ORD (I'll believe it before I see it though...). Problem is, ORD is so wicked busy that it doesn't take much to gum up the works. With as much traffic coming in/out of ORD at a given time, one airplane taking too long to taxi off of the runway can delay a whole string of flights. Currently, flights at ORD arrive in "banks" to enable shorter connections. Your flight from YVR is likely scheduled to fit into one of those banks. Moving it back 45 minutes would probably push it out of that bank, making connections difficult. It would probably just be delayed off of that scheduled time as well.

dcutcher

exactly what types of "weather" seriously affect airport traffic, and why. I can see that falling snow, or sleet, or hail, for example, would at least add de-icing/de-snowing to the departure schedule. Gusting winds conceivably would affect both arrivals and departures. But rain? Fog? Mist? Smog (here in ellay)? Didn't the technogods give us radar to deal with those problems so we could laugh in the face of Old Man Weather as we jet off to meteorlogically milder locales? (Then there's the matter of "climate...")
Some time ago, Ontario airport (ONT) boasted having an especially large inverted radar "cone" that allowed activity greater than typical at other, less well-equipped airports. So if ONT can, why can't...?

tjl

Some of the answer is airport dependent. Some airports are forced to close runways for conditions that other airports do not have to close runways for. For example, SFO has two parallel runways that are close together. In clear weather, they can both be used at the same time. In foggy or cloudy weather (common), only one can be used at a time. When that happens, delays build up through the day.

LarryJ

The answer to that is quite complex. There are many reasons why visibility restrictions can reduce an airport's acceptance and departure rate.

One reason is the spacing between parallel runways. On closely spaced runways you can run simultaneous approaches when the airplanes have each other in sight but lose that ability when they do not. That requires increased spacing and a reduced arrival rate. A few airports are now starting to use the new PRM approaches which helps.

There are many details which vary from airport to airport which can make a big difference in how much reduced visibility, or low clouds, might effect the arrival/departure rates. Same thing with wind. In some wind conditions you don't have as many runways avialble as you would with more favorable winds. You can also lose the ability to land, or depart, on particular runways in low visibility do the visibility requirements of that particular runway. i.e One runway might allow landings with 1/2 mile vis while a second runway may need 3/4 mile.