capacity to 36 arriving aircraft per hour. In poor visibility conditions, FAA instrument approach rules require aircraft to maintain lateral separation of 4,300 feet (1,300 m), meaning only one runway may be used, reducing the capacity of SFO to 25-30 arriving aircraft per hour. During rainstorms (approximately 4% of the time), the prevailing winds shift to a south-southeasterly direction, and departing aircraft use Runways 10L and 10R, and arriving aircraft use Runways 19L and 19R. This configuration is known as the Southeast Plan. On rare occasions (less than one day per year, on average), wind conditions dictate other runway configurations, including departures and landings on Runways 10L and 10R, departures and landings on Runways 1L and 1R, and departures on Runways 19L and 19R and landings on Runways 28L and 28R. Based aircraft and operations In 2019, SFO had 458,496 aircraft operations, an average of 1,255 per day. This consisted of 86% scheduled commercial, 11% air taxi, 2% general aviation and <1% military. There were 14 aircraft based at SFO, 6 jets, 1 helicopter and 7 military aircraft. Aircraft noise abatement SFO was one of the first airports to implement a Fly Quiet Program, which grades airlines on their performance on noise abatement procedures while flying in and out of SFO. The Jon C. Long Fly Quiet Program was started by the Aircraft Noise Abatement Office to encourage airlines to operate as quietly as possible at SFO. SFO was one of the first U.S. airports to conduct a residential sound abatement retrofitting program. Established by the FAA in the early 1980s, this program evaluated the cost-effectiveness of reducing interior sound levels for homes near the airport, within the 65 CNEL noise contour. The program made use of a noise computer model to predict improvement in specific residential interiors for a variety of noise control strategies. This pilot program was conducted for a neighborhood in South San Francisco and success was achieved in all of the homes analyzed. The costs turned out to be modest, and the post-construction interior sound level tests confirmed the predictions for noise abatement. To date over $153 million has been spent to insulate more than 15,000 homes in the neighboring cities of Daly City, Pacifica, San Bruno, and South San Francisco. Terminals The airport has four terminals (1, 2, 3, and International) and seven concourses (Boarding Areas A through G) with a total of 115 gates