The number of people in the security line is dependent only upon the rate at which they are processed and the total number arriving for their flights, doesn't depend upon how early people get there. And once people get through the lines, there's no change from before so there'd be no large increase in how many people are in the waiting areas. (Except for the increase in uncertainty in how long the lines will take, that will cause some extra people in the waiting areas. I see no reason to expect this to be a large enough effect to be problematic.)
Sorry, I don't understand. I'm contesting your claim that airports would have to hold more people than they currently are if people showed up earlier to account for the longer lines.
Let's say everyone shows up to the airport 3 hours before their flights. At 9:00 on Monday, the airport holds all people with flights departing between 9:01 and 12:00 -- 3 hours' worth of people.
Now you change that, asking people to show up 24 hours before their flights. At 9:00 on Monday, the airport holds all people with flights departing between 9:01 Monday and 9:00 Tuesday -- 24 hours' worth of people, eight times as much.
Airports can't hold 8x as many people without being in violation of the fire code.
Your numbers are exaggerated to make a point, but I think it actually changes things. My claim is that the airports are already holding the extra people, compared to before the wait time increase. They're waiting in line to get through the TSA checkpoint. Getting there early enough to make your flight doesn't change this: you still spend the same amount of time in the line, then go to your gate and board your flight.
Unless everyone is abandoning the line and going home since they're going to miss their flight (unlikely).
