A violent brawl erupted on a passenger jet when a man wearing a plastic face shield refused to wear a mandatory mask underneath and was told to leave, witnesses claim.

Video posted online shows several men fighting on the Allegiant Air flight with one is put in a headlock and another shouting after hitting him: “I will f***ing kill you.”

A ground crew worker desperately tries to break up the brawl – pleading “sir, sir, please” – but her efforts are futile and she is forced to take a step back and call for help on her radio.

Fellow passenger Rylie Lansford, who recorded the video, said “all hell broke loose” and the situation was “absolutely insane” because it was all due to a row over a face mask.