As passengers waited to board a British Airways flight bound for Austin, Texas, one woman demanded the hat was taken off, which bore the slogan of the Republican US Presidential canidate Donald Trump. 

When the woman wearing the hat refused, it was reported punches were exchanged in front of passengers in Terminal 5 and it held up departure for two hours.

The row continued on board, with reports suggesting the pair squared up to each other in the premium economy cabin. The captain called for assistance and both were escorted off the airplane by police, while the brawl continued.

A Heathrow source said the scene was extraordinary, having never recalled a flight delay due to a cap.

The Sun reported the source said: “With the US Presidential election so close, tensions are sky high. Airline crew could not run the risk of a full scale punch-up at 30,000ft."

The women were not arrested but were questioned by police, with both making claims of affray against each other. The Metropolitan Police confirmed that a probe into the incident is ongoing.

A spokesman for the force said yesterday: “Shortly after 12.45pm on Monday, October 28, police at Heathrow were made aware of an incident involving two women waiting to board a plane in Terminal 5.

“A woman in her 40s and a woman in her 60s made counter allegations of affray.

“Enquiries are ongoing.”

Flight BA191, originally scheduled to depart at 12.10pm, took off at 2.11pm without the two women on board.

The U.S. presidential election is scheduled for November 5 between Donald Trump and Kamala Harris, with polls predicting an extremely tight race.