we spoke with amick airport worker as he came up to pick up his car at the end of his shift. it is parked right next to the two that were smashed. your part here. lucky. so that hopefully, this guy is insured. >> reporter: no one was injured on the ground when the tire came crashing down. while on site we saw in the united employee taking pictures of the damage. a large tire else into a rental car agency lot and police were able to get to it pretty easily it is since been removed from the scene. we counted two crunched cars and another employee told us there was another crunch car -smashed car or damage, if you will, inside the slot. at least three vehicles damaged when the tire came off and bounced and ultimately came to a rest. thankfully, the flight took off around 11:00 in the morning, which is about the time when most employees are at work at san francisco. is a good thing there were no injuries. reporting live at san francisco i am sergio quintana, nbc bay area news . >> 250 pound tire. let's bring in ian cull. how could this happen? we spoke with aviation experts this