Federal officials said Wednesday they have completed outfitting 43 major U.S. airports with technology to warn when incoming planes are aimed at a taxiway instead of a runway.

The Federal Aviation Administration said the system's software predicts when a plane is lined up to land on a taxiway and sends an alert to air-traffic controllers.

None of the recent close calls between planes have involved aircraft lined up incorrectly to land on a taxiway, but that type of error nearly resulted in disaster at San Francisco International Airport in 2017.

The National Transportation Safety Board recommended the technology change after the San Francisco incident in which an Air Canada jet nearly crashed into four other planes on a taxiway at night.

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The safety board also recommended that the FAA require planes landing at major airports have systems to alert pilots if they are not lined up with a runway. The FAA said it is still considering that recommendation. Commercial planes already have other equipment to help pilots line up with runways at big airports.

Taxiways are paved surfaces that planes use to get in position for takeoffs or taxi to the terminal after landing. Most cases of planes landing on taxiways involve "general aviation"—privately owned small planes—but 16% involve commercial flights, according to the FAA.