The Federal Aviation Administration (FAA) (defendant) published a “Notice to Operators” in the Federal Register, in which it required certain Alaskan hunting and fishing guides who pilot light aircraft to abide by FAA regulations for commercial air organizations. For thirty years prior to the publication of the Notice, and based on its interpretation of Administrator v. Marshall, 39 C.A.B. 948 (1963), the Alaskan Region of the FAA consistently advised guide pilots that they were not governed by the regulations controlling commercial pilots. A guide organization and individual guides (plaintiffs) petitioned for review, arguing that the Notice altered the FAA’s well-established interpretation of its regulations and should have been promulgated in accordance with the notice and comment requirements of the Administrative Procedure Act (APA). The FAA argued that the Alaskan Region misread Marshall and that the Notice did not fundamentally change any authoritative interpretation of its regulations.