Here's the full text of 4a, see for yourself:
>The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
There are no exceptions in there for air travel! It's incredibly firmly worded, and is obviously deliberately meant to be very restrictive on government power.
They don't have probable cause to search every single person, let alone a warrant to do so. And their holding people's freedom to travel hostage to do so, and conditioning Americans to a lack of rights that were supposedly enshrined in the Bill of Rights.
The notion that they need to search every single person flying is not remotely "reasonable". It's one more step towards a police state. It's a shame that the 4th amendment isn't defended as strongly as the 1st & 2nd. The patriot act is the reason why flying sucks now when it used to be fantastical.