San Francisco International Airport We arrived at SFO three hours before our flight to allow time for security check. The security was strict. Our carry-on items were checked the second time at the gate before boarding. Our BA flight departed SFO around 5:20 p.m. It was delayed for 30 minutes because two passengers did not get on the plane and their luggage had to be off loaded. The air got really stuffy inside the plane since they couldn't turn the AC on full blast until take off.