FAA falls nicely under the Commerce Clause.
Post Roads may actually be better. (The original air routes were actually air mail routes, and a lot of mail still goes by plane.)
http://sometimes-interesting.com/2013/12/04/concrete-arrows-and-the-u-s-airmail-beacon-system/. (The original air routes were actually air mail routes, and a lot of mail still goes by plane.)
Note that President Madison likewise agreed with the 14th Congress that the roads and canals that Congress wanted to build when it drafted the public works bill of 1817 would be a good thing for both the General Welfare and Defense of the country.
But also consider that he wrote his agreement with Congress in the constitutionally required veto explanation to Congress, Madison also pointing out in the veto explanation that roads and canals were not among Congress’s Section 8 powers regardless of arguments about the postal roads clause (1.8.7).
Veto of federal public works bill, 1817
In fact, a later generation of state sovereignty-respecting justice had effectively justified Madison’s veto with the following clarification of the fed’s constitutionally limited powers — powers not expressly delegated are prohibited.
”From the accepted doctrine that the United States is a government of delegated powers, it follows that those not expressly granted, or reasonably to be implied from such as are conferred, are reserved to the states, or to the people. To forestall any suggestion to the contrary, the Tenth Amendment was adopted. The same proposition, otherwise stated, is that powers not granted are prohibited [emphasis added].” —United States v. Butler, 1936.
What patriots are overlooking (ignoring?) is that there was nothing stopping the 14th Congress, or any later generation of Congress, from petitioning the states for a roads and canals amendment to the Constitution after Madison’s veto of that bill.
Hypothetically speaking, if the states had given Congress the roads and canals constitutional amendment that it wanted, Congress could have then asked President Madison, “There, are you happy now?” while Madison signed the bill based on constitutionally enumerated powers.
Regarding Madison’s narrow interpretation of the Commerce and US postal roads clauses, Jefferson had previously expressed the following concern about interpreting the Constitution.
"In every event, I would rather construe so narrowly as to oblige the nation to amend, and thus declare what powers they would agree to yield, than too broadly, and indeed, so broadly as to enable the executive and the Senate to do things which the Constitution forbids." --Thomas Jefferson: The Anas, 1793.