under the radar

An allusion to flying an airplane at an altitude too low for radar detection.

• Audio (General Australian):

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under the radar

1. (idiomatic) Without attracting notice; in an undetected or secretive manner.
   • 2004 August 30, Andrea Sachs, “About-Face”, in Time:

     Institutional change has not happened. But it's done quietly under the radar at lots of places.

   • 2022, Liam McIlvanney, The Heretic, page 48:

     Look, we keep our hand in with Maitland as well as this Partick thing. But we do it under the radar.

• See also Thesaurus:covert

• fly under the radar
• slip under the radar