FAA has issued airworthiness directive 2021-17-08 for certain Boeing 737-800s and -900ERs, requiring de-modification of a certain supplemental type certificate installation by removing external equipment including radome, antenna and associated structure, installing doubler and fasteners, and system deactivation by pulling and collaring associated circuit breakers if installed, plus inspecting the external and feed-through doublers, intercostals, skin and frames in the area around the removed external equipment for cracking, and repair if necessary, effective Aug. 17, 2021.