United Airlines is conducting an internal investigation after one of its captains diverted a flight to deplane a senior flight attendant who he argued with.

Flight 842 from Sao Paulo, Brazil to Chicago O'Hare diverted to Miami early in the morning of 14 July midway through the scheduled 6hr 45min non-stop flight.

A source familiar with the incident says the captain ordered the purser of the Boeing 767 to leave the aircraft because he was "not respecting his authority".