If you want to get all strict-constructionist on this matter though, planes, cars, buses, and rail didn't even exist when the Constitution was written, so one could argue that there's no Constitutional protection when travelling by anything beyond horseback, carriage, or walking.
No you cannot argue that. The Constitution says nothing about technology and everything about how humans behave.
Then there's the other side, where airlines were allowed to be in charge of their own security, letting "the market" set the balance, but then nineteen men decided to kill about 3500 men, women, and children one day, and our society realized that it wasn't gonna work to let the airlines be in charge of security.
That strategy ceased to be effective at 9:03AM on 9/11/2001 over a field in Shanksville, PA. And you know who figured that out? Ordinary Americans, doing the security calculus themselves, where the government had completely failed to protect them, despite having many opportunities to do so.
To be double-sure the airlines all secured their cockpit doors. That risk no longer exists, which is why the TSA has never caught a terrorist. They do violate the human rights of Americans all day, every day. In an effort to stop the terrorists, they have become the terrorists, all because they consciously choose to violate the highest law of the land.