Recently, the Federal Aviation Administration (FAA) issued a safety alert for operators (SAFO) called “Night Vision Goggle (NVG) Advisory Pertaining to Certain Red Color LEDs.” This SAFO advises operators using NVGs that certain LED lighting systems fall outside the combined visible and near-infrared spectrum of NVGs, and thus will not be visible to them.
The alert points out FAA requirements for "Aviation Red" light ranges from about 610-700 nm, and NVGs approved for civil aviation are only sensitive to energy ranging from 665 to ~930 nm. Crews that fly using NVGs are warned to use extra caution when flying near obstacle areas. The FAA recommends training for NVG users, to advise pilots of the limitations outlined in this SAFO.
It’s known that the Canadian Air Force’s Directorate of Flight Safety issued a Flight Safety Flash last year, Which showed some red obstruction LED lighting systems were clearly visible to the naked eye but not visible to NVGs.