No, it’s not illegal to display the U.S. flag upside down
The U.S. flag code says American flags should not be displayed upside-down except as a signal of “dire distress,” but free ...
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Jets accidentally bring team banner out upside down in pregame display
Before the game, the Jets flag crew emerged holding the team flag, only to realize that it was upside down and facing toward the end of MetLife Stadium opposite from where it should've been.