Fly beneath (the/someone's) radar phrase
To go without being aware of or being paid attention to by someone or by people in general.
That pupils smoke at school is flying beneath the teachers' radar.
I can't let such a heinous crim fly beneath the police's radar.
For the first 5 years of its existence, the organization flew beneath the authorities' radar.
The verb "fly" must be conjugated according to its tense.
This phrase was formed based on the meaning of the phrase "under the radat", which dates from the World War II.