II. SFO - Reducing Delays by Reducing Arrival Rates
SFO suffers delays in good weather and bad when a large number of planes arrive in a short period of time. These spikes in demand are the result of:
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Scheduling more flights than the airport can accommodate under ideal conditions·
Scheduling a large number of flights to arrive or depart at nearly the same time·
Allowing a high volume of small propeller driven commuter planes
United Airlines intentionally operates a large number of flights on smaller planes to keep competitors out of its hub at SFO. SFO’s Delay Study 6 reported that United explained, "if it were to reduce its LAX-SFO service frequency by the amount implied by our recommendation, its competitors would jump into the market, filling the time slots opened up." The Delay Study further found that United's approach is to "schedule more flights than SFO can accommodate on many days and then cancel the ones you can't operate."
During Summer 2000, United operated 38 SFO-LAX roundtrips using Boeing 737 aircraft seating only 134 passengers. United opted to use smaller jets even though SFO’s Delay Study found that, "larger aircraft are more fuel efficient on a per seat basis, and they generally also reduce crew costs per seat. They also reduce noise and air pollution." SFO-LAX flights departed at a rate of one plane every 27 minutes. If United had used larger 200 seat aircraft, it could have moved just as many passengers while eliminating at least a dozen flights per day. Even with a reduced number of flights, it could have maintained a frequency of one departure every 42 minutes.
On a typical morning, SFO has at least 13 flights scheduled to depart at exactly 7 a.m. even though the departure rate at SFO is less than one plane per minute (47 planes/hour). It would take 17 minutes for these 13 flights to depart under the most ideal conditions. SFO’s Delay Study found that there are four concentrations of arrivals each day that exceed the airport’s maximum capacity to accept arrivals. One concentration results in 20 planes being scheduled to land in 15-minute period even though the airport can only handle one arrival per minute under ideal conditions. These scheduling practices guarantee delays.
Commuter planes operating out of SFO account for 18% of the flights but carry only 3% of the passengers. The commuter planes, typically seating 30 passengers, serve smaller communities such as Eureka, Sacramento, Monterey, Modesto, and Santa Rosa. These smaller planes actually take up more time and space in the pattern because they are slower and must follow farther behind large jets to avoid turbulence. Officials at La Guardia Airport calculate that they can land two large jets in the time it takes for three commuter planes to arrive.
SFO can reduce delays in all weather conditions by:
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Spreading arrivals and departures more evenly·
Using larger planes to reduce the total number of flights·
Reducing the number of commuter flights
While the rate of scheduled arrivals at SFO can exceed the arrival capacity of 60 planes/hour, the average rate of arrivals at SFO during all peak hours (6 a.m. to 10 p.m.) is only 34 planes/hour . If arrivals were scheduled more evenly, delays would be reduced. The current spike in arrival demand at 10 a.m. is especially problematic because fog conditions at SFO usually linger until 10 a.m. but clear before 11 a.m.
Although SFO is one of the nation’s busiest airports, only 31% of its passenger flights use planes that seat more than 150 passengers. While logic would dictate a shift to larger aircraft, the Runway Reconfiguration Study predicts minimal shifts by the airlines.
Commuter flights from cities located within 100 miles of San Francisco (Monterey, Modesto, Sacramento, Santa Rosa) could be reduced or eliminated. Other cities with multiple small plane flights to/from SFO could have a reduced number of flights using larger planes. Passengers who arrive primarily to connect to other flights from cities like Fresno could opt to either arrive early on a larger plane or make their connection through another airport like LAX. Residents of the Bay Area need to balance the environmental and economic cost of filling the Bay against maintaining high levels of service to outlying communities that benefit a small number of people.
8 Reducing Weather-Related Delays and Cancellations at SFO, Charles River Assoc./John F. Brown Co.
9 Calculated from Exhibit 15 (Scheduled Operations by Hour), Regional Airport System Plan (2000)