St. Louis County, MO Noise Ordinances: Aircraft Noise (2026)

Section 625.020(26) defines a "stationary noise source" to expressly include "any equipment, motor vehicle, aircraft, or facility, fixed or movable, capable of emitting audible sound," bringing aircraft on the ground within the Noise Control Code's reach. Section 625.070 then exempts most aircraft operation: "The inflight operation of aircraft, including the pre-takeoff run-up of aircraft engines" is not subject to the chapter, "provided, however, with the exception of the pre-takeoff run-up of aircraft engines, the provisions of this chapter shall apply to the run-up of aircraft engines, mounted or unmounted, for maintenance or test purposes during nighttime hours." "Nighttime hours" is defined at Section 625.020(18) as 10:00 p.m. to 7:00 a.m.

So a mechanic testing or maintaining an aircraft engine on the ground after 10 p.m., whether the engine is still mounted on the airframe or removed for bench testing, must keep the noise at or below the applicable Table I limit measured at the property boundary, the same numeric standard the Code applies to any other stationary commercial or industrial noise source. Daytime maintenance run-ups and any pre-takeoff run-up at any hour remain outside the Code entirely, and in-flight noise is never covered no matter the hour.

The Code applies countywide in unincorporated St. Louis County and in incorporated cities under 75,000 population that haven't adopted their own equally strict noise ordinance, per Section 625.030.