The plaintiffs challenged the CDC’s pandemic-era transportation mask requirement issued after President Biden’s COVID-19 emergency directives. While the appeal was pending, the public-health emergency ended and the mandate expired, eliminating the live controversy; the Eleventh Circuit also rejected the argument that the dispute was likely to recur for these parties. Following the ordinary Munsingwear rule for a case mooted on appeal, the court vacated the district court’s judgment and instructed it to dismiss the case as moot.