The question posed—whether a single 91.147 letter of authorization can cover air tour operations from multiple base airports, each with its own 25-statute-mile radius—touches on a regulatory gray area that many small commercial operators encounter as they scale beyond a single-airport footprint. FAR 91.147 governs "nonstop Commercial Air Tours" conducted for compensation within a 25-mile radius of the airport of takeoff, requiring the operator to hold a Letter of Authorization (LOA) from the FSDO rather than a full Part 135 certificate, provided the flights stay within that radius and meet other limiting criteria (no international operations, specific aircraft/passenger limits under related exemptions, etc.). The regulation and its associated guidance in FAA Order 8900.1 are written with a single-airport model in mind, and the text itself does not explicitly address multi-base operations, which is exactly the ambiguity the original poster is running into. In practice, this kind of question typically gets resolved not by parsing the CFR text alone but by direct coordination with the local FSDO, since LOAs are issued at the discretion of the FAA and can be tailored—or restricted—based on how the operator's application is structured.
For working pilots and operators in the air tour segment—helicopter tour companies, seaplane operators, and small fixed-wing sightseeing outfits—this matters because 91.147 is the low-barrier-to-entry pathway that lets small businesses run scenic flights without the cost and complexity of a full Part 135 certificate. Many of these operators are single-owner or small-fleet businesses that want to expand seasonally or geographically (e.g., a summer base in one location and a winter base in another, or multiple simultaneous bases to serve different markets like Hawaii inter-island tours or western U.S. canyon/mountain tours). Whether the FAA will issue one LOA covering multiple bases, require separate LOAs per base, or push the operator toward a Part 135 certificate once operations reach a certain scale is a decision that can significantly affect the operator's cost structure, insurance requirements, and operational complexity. Getting this wrong—operating tours from an unauthorized base or outside the scope of an LOA—exposes the certificate holder (and potentially the PIC) to enforcement action, since air tour operations sit under increased FAA scrutiny following historic accidents in the sightseeing sector (Grand Canyon, Kauai, and similar high-profile events) that have driven tighter oversight of both 91.147 and Part 135 tour operators.
This also reflects a broader trend of FAA regulations struggling to keep pace with how modern small commercial operators actually structure their businesses. Air tour operators, drone survey companies, and other niche commercial segments frequently find that the regs were drafted around a simpler, single-location operational model, forcing operators into individualized negotiations with their FSDO to get authorizations that fit multi-site business plans. The FAA has periodically revisited air tour rules—including safety-focused NPRMs and the National Parks Air Tour Management Act framework for tours over federal lands—but administrative mechanics like multi-base LOAs remain under-addressed in public guidance. For pilots and operators pursuing this kind of expansion, the practical takeaway is that the answer will almost certainly come from a conversation with the FSDO's air tour or GA operations unit rather than from CFR text alone, and operators should be prepared to submit separate risk assessments, competency/training documentation, and possibly separate LOAs for each base to satisfy the FAA that risk management, weather reporting, and local hazard awareness are adequately addressed at each location.
Finally, this scenario underscores the value of engaging aviation counsel or a former FAA inspector/consultant experienced in 91.147 operations before assuming a single LOA can be stretched across multiple physical bases. Because LOAs are discretionary and locally issued, precedent from one FSDO doesn't bind another, meaning an operator with multi-base ambitions should expect to build a case specific to their aircraft, routes, and markets rather than relying on anecdotal answers from online forums—useful as those discussions are for surfacing the question in the first place.