Another Day of Storm-Related Delays at SFO

It's been a particularly trying week for airline passengers flying to or departing from San Francisco International Airport, with long flight delays and scores of canceled flights.

The busy facility always faces challenges during summer fogs and winter storms. That's because the airport typically uses a pair of parallel runways to land planes. In clear weather, planes are allowed to land two at a time, virtually side by side; when visibility is impaired by low clouds or heavy rain, arriving flights can land just one at a time. That cuts the airport's capacity by half, and in really unfriendly weather, even more than that.

The reduction in capacity, in turn, prompts the Federal Aviation Administration to impose what it calls a ground-delay program.

Instead of allowing flights to just take off when there's bad weather at the destination, the FAA holds them at the departure airports. Then, the air-traffic control system performs what amounts to a massive rearrangement of flight schedules. Planes are assigned specific departure times and allowed to take off only as fast as the bad-weather airport can receive them. It's a form of metering that tries to prevent arriving jets from getting stacked up at their destinations and having to circle waiting for the chance to land.

The impact of all this plane-juggling on SFO this week has been dramatic.

On Tuesday and Wednesday, flights destined for SFO were delayed four hours or more. On Thursday, even as our Dramatic December Deluge moved out of the areas, flights bound for San Francisco were delayed about 40 minutes.

And of course, the problems go beyond delays. Holding up flights for hours on end is smart management from an air-traffic-safety perspective, but it plays havoc with airline schedules, which typically rely on using arriving planes for trips to new destinations.

For instance, your flight to Los Angeles or Seattle might depend on a plane coming from O'Hare in Chicago. If that flight from O'Hare can't take off -- well, the best you can hope for is a long delay. And often, your best hope will be in vain: Your flight on that long-delayed jet will just be canceled.

Thursday morning, 19 flights were reported canceled -- 12 arrivals and seven departures. That was a minor impact compared to Wednesday, when SFO recorded more than 90 cancellations. A similar number of flights were scrubbed on Tuesday.

Delays at the Bay Area's other major airports have been minimal. Oakland International reported no flight delays this week. Mineta San Jose International was forced to divert some flights Monday night due to fog, but has operated with only minor delays since then.