Executive Decision (1996)

Suggested correction: To answer the first part of your question, it is made clear in the movie that the cameras can be rotated. They are using very small probe cameras that the operator can simply rotate by hand. However, some of the cameras have obstructed views, depending on where they were trying to look. The camera that Rat was on could not see the sleeper's face, because the overhead baggage compartment was in the way. Louie's camera was overhead just a few seats behind the guy who was mistaken for Demou, but still several rows ahead of where Demou actually was. When Grant made his move for Demou, Louie simply rotated the camera and was able to see. To address your second point, they had many cameras throughout the plane. However, they did not have a clear view of all 400 passengers faces. Not to mention, they were running short on time. Furthermore, Grant told Jean that she should be looking for someone with an electronic device, which is something that the team would likely not be able to see from the probe cameras. Jean would be able to see an electronic device a lot easier as she made her way through the cabin, which she did. (it turned out to be the wrong device, but that's beside the point).