What is a potential consequence if a foreign airline does not receive approval from U.S. authorities to operate in U.S. airspace?

If a foreign airline does not receive approval from U.S. authorities to operate in U.S. airspace, the consequence is that they will be barred from entering the market. The U.S. has strict regulatory requirements for foreign carriers wishing to operate flights to and from its airports, which includes obtaining a necessary certificate of authorization from the Department of Transportation (DOT) and compliance with safety and security regulations established by the Federal Aviation Administration (FAA).

Without this approval, the airline cannot legally schedule or conduct flights within U.S. airspace, effectively barring them from accessing the significant U.S. aviation market. This regulatory framework ensures that foreign airlines meet the same safety and operational standards as domestic airlines, which is critical for maintaining safety, security, and the integrity of the air transportation system.

The other options reflect misunderstandings about the implications of operating without the appropriate authorization. Modifying a fleet would not be a direct consequence of denial of approval; appealing to the U.S. Supreme Court is not a viable option for this type of administrative decision; and temporary authorization is only granted under specific circumstances, typically after an application process, not as a fallback if denied initial approval.