Which provision in the constitution allowed congress to establish an air force?

Article I, Section 8, Clause 12 of the US Constitution.

Explanation:

Although the US Constitution does not explicitly outline that the government is allowed to establish an air force like it allows it to establish land and naval force, it does states in Article I, Section 8, Clause 12 that it has the power “To raise and support armies” which provides for the creation of military forces in general, including an air force.

the answer is b: an economic crisis throughout the country.