I would be more worried about someone bombing the security line at a major airport than about bombing a plane. I would also worry about the access to glass in an airport -- ask any prisoner if you are wondering why.
"the only alternative is to over-protect to some degree"
You are still assuming that the TSA's airport checkpoint program is protecting us at all, which I would say is a dubious claim at best. Locking the cockpit doors on an airplane is a good measure. Putting an armed guard on certain high-value target flights is a reasonable measure, although I would be a bit concerned about a clever terrorist's ability to identify the guard and take his weapon. Screening luggage for bombs is reasonable, although I think an airport is just as good of a target for bombing as an airplane would be, so I am not sure how much good it does.
The checkpoints, however, are next to useless for security. There is an endless supply of things that can be turned into weapons on the other side of a security checkpoint, and you don't have to be an evil mastermind to find them. They even let you bring dangerous items through the checkpoint, like the 9-cell lithium-ion battery in my laptop (would you want to be on an airplane where someone punctured or ignited such a battery?) -- for that matter, the laptop itself, which has lots of sharp aluminum inside and which could be disassembled fair easily.
What the checkpoints do is to remind people that they are not in charge and that their rights mean nothing at the airport. I had this experience myself, twice. First, I was told that I could had to wait over 10 minutes to receive a pat-down after refusing to walk into a scanner, and that I would not be allowed to use the metal detector that just opened -- all the while, my luggage was left on the other side for anyone to steal. The second time, my teammate who traveled with me tried to take a video recording of the pat-down procedure, and the guard stopped (but did not allow me to put my arms down), claiming that it was necessary for security to not let a video be taken (but when I pointed out that there were literally dozens of people watching from the waiting area ten feet away, his eyes glazed over -- he was just reciting the line some superior had told him to recite). These are not measures that enhance security, but they certainly are a psychological attack; I doubt they are carefully planned attacks, but rather they are an intended consequence of giving people who have absolutely no training in security or threat mitigation the power to make decisions at a security checkpoint.
"the only alternative is to over-protect to some degree"
You are still assuming that the TSA's airport checkpoint program is protecting us at all, which I would say is a dubious claim at best. Locking the cockpit doors on an airplane is a good measure. Putting an armed guard on certain high-value target flights is a reasonable measure, although I would be a bit concerned about a clever terrorist's ability to identify the guard and take his weapon. Screening luggage for bombs is reasonable, although I think an airport is just as good of a target for bombing as an airplane would be, so I am not sure how much good it does.
The checkpoints, however, are next to useless for security. There is an endless supply of things that can be turned into weapons on the other side of a security checkpoint, and you don't have to be an evil mastermind to find them. They even let you bring dangerous items through the checkpoint, like the 9-cell lithium-ion battery in my laptop (would you want to be on an airplane where someone punctured or ignited such a battery?) -- for that matter, the laptop itself, which has lots of sharp aluminum inside and which could be disassembled fair easily.
What the checkpoints do is to remind people that they are not in charge and that their rights mean nothing at the airport. I had this experience myself, twice. First, I was told that I could had to wait over 10 minutes to receive a pat-down after refusing to walk into a scanner, and that I would not be allowed to use the metal detector that just opened -- all the while, my luggage was left on the other side for anyone to steal. The second time, my teammate who traveled with me tried to take a video recording of the pat-down procedure, and the guard stopped (but did not allow me to put my arms down), claiming that it was necessary for security to not let a video be taken (but when I pointed out that there were literally dozens of people watching from the waiting area ten feet away, his eyes glazed over -- he was just reciting the line some superior had told him to recite). These are not measures that enhance security, but they certainly are a psychological attack; I doubt they are carefully planned attacks, but rather they are an intended consequence of giving people who have absolutely no training in security or threat mitigation the power to make decisions at a security checkpoint.