What Part 137 covers
14 CFR Part 137 — Agricultural Aircraft Operations — applies to any person who uses an aircraft for the purpose of dispensing substances for agricultural purposes. This includes spraying pesticides, herbicides, and fungicides; seeding crops or reforestation areas; applying fertilizer; and dispensing fire-retardant materials for forest firefighting (when classified as agricultural operations).
Part 137 creates a separate regulatory framework because agricultural flying involves operations — particularly low altitude and dispensing — that would be prohibited under standard Part 91 rules. The regulations establish operator certification, pilot qualification, aircraft requirements, and operational limitations specific to the unique demands of aerial application.
The regulation distinguishes between operations over non-congested areas (14 CFR 137.29-137.35) and operations over congested areas (14 CFR 137.51-137.53), with the latter requiring additional FAA authorization and more stringent safety measures.
Operator certification and ag pilot requirements
To conduct agricultural aircraft operations commercially, an operator must hold an Agricultural Aircraft Operator Certificate issued by the FAA under 14 CFR 137.11. The application requires demonstrating the means to comply with all applicable regulations, including having properly certificated pilots, airworthy aircraft with required equipment, and operational procedures that meet FAA standards.
Pilot qualifications under Part 137 require at minimum a commercial pilot certificate with the appropriate category and class rating for the aircraft to be used. Beyond the certificate, 14 CFR 137.19 requires the pilot to demonstrate competency to an FAA inspector or designated examiner in the specific aircraft type used for agricultural operations, including short-field and soft-field operations, appropriate speeds and altitudes for dispensing, procedures for handling economic poisons, and emergency procedures specific to low-altitude operations.
The pilot must also possess knowledge of the applicable FARs and the effects and safe handling of materials being dispensed. This includes understanding toxicity levels, drift characteristics, buffer zone requirements, and proper decontamination procedures. Many states impose additional licensing requirements for aerial applicators beyond the federal standards.
Aerial application operations
Agricultural flying is among the most physically demanding and technically challenging forms of commercial aviation. A typical application flight involves repeated passes at 8 to 15 feet above the crop canopy, with turns at the end of each swath that may involve bank angles of 60 degrees or more at airspeeds of 100 to 140 knots, all while managing the dispensing system and avoiding obstacles.
Spraying involves liquid application through nozzles mounted on booms attached to the trailing edge of the wings (fixed-wing) or the belly (helicopter). Droplet size, spray pressure, airspeed, and height above the target all affect coverage uniformity and drift. Wind speed and direction are critical — drift of pesticides onto non-target areas is both an environmental and legal liability. Most operations halt when surface winds exceed 10 to 12 knots or when temperature inversions trap chemical drift near the surface.
Seeding and fertilizing use a spreader or granular dispersal system. The dispensing rate is calibrated based on airspeed, swath width, and the desired application rate per acre. GPS-based guidance systems have become standard in modern ag aviation, enabling precise swath tracking, variable rate application, and documentation of treated areas.
Loading and turnaround operations at the airstrip or loading site present their own hazards. Chemical handling, rapid fueling, and the pressure to minimize ground time create risks that must be managed through established procedures. The loading area should be positioned to allow takeoffs into the wind with adequate runway or strip length.
Congested area operations and operating over people
Standard Part 137 operations (14 CFR 137.29) permit dispensing operations over non-congested areas at altitudes below those prescribed by Part 91, provided the operation is conducted without creating a hazard to persons or property on the surface. This exemption from Part 91.119 minimum altitudes is essential because effective aerial application requires flying at very low altitudes.
Operations over congested areas require a specific amendment to the operator's certificate under 14 CFR 137.53. The FAA evaluates the applicant's ability to conduct these operations safely, considering the pilot's experience, the equipment to be used, and the specific operating procedures proposed. Congested area operations must not be conducted over any congested area unless the operator holds this authorization.
14 CFR 137.33 specifically addresses the requirement that no person may dispense any substance in a manner that creates a hazard to persons or property on the surface. This goes beyond the standard Part 91 careless and reckless provision (91.13) to specifically address the dispensing aspect of agricultural operations. Violations can result in certificate action and civil penalties.
Operating near people, structures, and public roads requires careful planning. Buffer zones between the treatment area and sensitive areas (residences, schools, waterways) may be mandated by the product label, state regulations, or both. The applicator is responsible for compliance with all applicable federal, state, and local regulations — not just the FARs.
Aircraft requirements and the restricted category
Aircraft used in agricultural operations must be airworthy and equipped for the specific operation. Many purpose-built ag aircraft are certificated in the restricted category under 14 CFR Part 21.25, which allows type certification for special purpose operations. Restricted category aircraft have operating limitations — they typically cannot carry passengers (other than required crew), cannot be operated over congested areas (unless specifically authorized), and must display "RESTRICTED" on the aircraft.
Common ag aircraft include purpose-built airframes designed for the demands of agricultural flying: corrosion-resistant materials, crashworthy cockpit structures, wire strike protection, quick-dump capability for the hopper in an emergency, and powerful engines that can sustain repeated high-power climbs at heavy weights. The FAA type certificate data sheet for each ag aircraft specifies the authorized dispensing equipment, maximum hopper loads, and operational limitations.
Standard category aircraft can be used for ag operations under certain conditions, but they lack the specialized safety features and structural reinforcement of purpose-built ag aircraft. 14 CFR 137.31 requires that the aircraft meet the requirements of its type certificate and be maintained in accordance with applicable regulations, including any supplemental type certificates for dispensing equipment.
Safety: the PAASS program and accident prevention
The Professional Aerial Applicators' Support System (PAASS) is a voluntary annual safety training program developed by the National Agricultural Aviation Association (NAAA). Each year, the PAASS program develops training materials focused on the leading causes of ag aviation accidents, and state agricultural aviation associations conduct PAASS training sessions across the country.
The ag aviation industry has made measurable safety improvements over the past three decades. The accident rate per 100,000 hours has decreased significantly, driven by pilot training programs like PAASS, GPS guidance systems that reduce pilot workload during application, improved aircraft design with enhanced crashworthiness, and greater awareness of human factors including fatigue management during the intense seasonal workload.
Despite improvements, ag aviation remains a high-risk occupation. The leading accident causes include wire strikes (power lines and cables during low-altitude operations), loss of control during pull-ups and turns at the end of swaths, spatial disorientation (particularly during early morning or late evening operations in marginal visibility), and mechanical failure during the high-stress operating environment. Fatigue is a significant factor — during peak season, ag pilots may fly 8 to 10 hours per day for weeks at a time.
The FAA Safety Team (FAASTeam) and the NAAA jointly promote safety resources including accident case studies, wire-marking programs with utility companies, and guidance on operational risk management. The industry's safety culture emphasizes that no job is worth taking unnecessary risk — a philosophy that has been reinforced by analysis of preventable accidents.