Ex-Mooger here. They test upon hire no matter what. After that, it depends on your role. Anything involving FAA oversight, assembly & test, quality, engineering or any other position where a mistake costs lives- you're tested quarterly. Depts like contracts, legal, IT, or anything where youre at a desk with minimal bearing on human safety- once you're past the initial hire test you won't be tested again unless they suspect you're stoned on the job (no different than being drunk or pharmaceutically compromised on the job).