SAN FRANCISCO (AP) — U.S. officials are investigating two more incidents at San Francisco International Airport where planes could have wound up on the same runway, the National Transportation Safety Board said Monday. The incidents include an event in December 2016 when a SkyWest plane crossed a painted runway line it was supposed to stay behind while another plane was taking off, according to a safety board preliminary report. The safety board report also revealed that a Compass Airlines plane in February was forced to abort a landing because a Virgin America jet was lined up and waiting to take off on the same runway.