The JCPOA era is coming to an end as the JCPOA is close to effective expiration. The US government obviously considers policy alternatives to the rapidly expiring JCPOA. One argument in favor of a no-fly zone over Iran is that it is relatively inexpensive to maintain. It is a cheap military alternative that does not require boots on the ground, does not lead to American casualties and is very sustainable in the long run. After the Israeli destruction of the Iranian nuclear weapons program will a US no-fly zone make it possible to continually attack Iranian nuclear installations and thus make it impossible for the Iranian nuclear weapons program to ever recover.
A no-fly zone is highly likely to help ignite armed rebellions with US air support against Persian Islamist domination in the ethnic periphery which makes up half the population of Iran. This will reduce Iran to Persia, deprive it of its Indian Ocean coastline, deprive it of most of its oil resources and remove half the population of Iran from the control of the regime. This will make it possible to impose a naval blockade at the Strait of Hormuz in effectively choking the regime economically as the rebel regions will control most of Iran’s borders.
In the best case scenario will a no-fly zone over Iran also lead to armed rebellion with US air support in Persian speaking areas as well, but this is far far less certain than in the ethnic periphery. There is however a high likelihood that the ethnic rebel regions will become model democracies as the highly secularized peoples of Iran crave freedom and representative government.
Conclusion: A no-fly zone is inexpensive to maintain and is by far the best policy alternative to the failed JCPOA.