very tight. guards posted up on different corners. different check points. you can see some of the memorials here in the reflection pools still here today. new yorkers will also see that tribute in light. that enormously remarkable spectacle, the two beams of light shining in the sky for miles to see. those are expected to come at sunset later today. boris, christi. >> laura jarrett, we thank you so much. cnn's darryl borgis is live in pennsylvania. when you look at the time line of things. the south tower collapsed at 9:59. the crash in pennsylvania was just four minutes later. what do we expect today?