ISn't the placing of the National Guard at the direction of the President and being paid for by the Federal Govt. a violation of the Posse Comitatus Act?

Only if they are acting in a law enforcement role, i.e. arresting people.

What about conducting interviews on the concourse and searching people? Is that not Law Enforcment. Just because they don't slap cuffs on them doesn't mean its OK. Not to mention if a Soldier with an M16 stops you doe you think you have an ability to leave freely? Under the Constitution that is arrest whether the word is said or not.

ADTECH, I'm not real sure on the wording of said Act.  But I see where you're coming from, not sure either of how the law is interpreted on use of NG for guarding things like airports.  It may depend on if the particular unit is "federalized", as there is a difference between NG units under the direction of the Federal Gov't and units directed by a state.  Don't ask me to provide details as that's about the extent of my knowledge on this subject.  Might try one of the lawyers in the legal section?

They are not federalized so itisn't a violation

Posse Coitatus does not apply to the National Guard when they are activated by the states. In the current case, they were activated by their respective governors, but the federal government is picking up the tab.

Most states have laws on the books (somewhere) about the powers and duties of the guard and other state militia forces when called into state service for emergencies, disasters and insurrections. Those laws usually include arrest, detention and search authority.

If they are activated by the federal government, then Posse Comitatus applies.