Southwest Airlines has said it will conduct an internal investigation into an incident where the pilot allegedly used a phrase to insult president Joe Biden.

       The pilot signed off an inflight announcement with the phrase “let’s go, Brandon” on Friday morning. The phrase has been used in Republican circles to target the president recently.

       The airline said it would “address the situation directly with any employee involved while continuing to remind all employees that public expression of personal opinions while on duty is unacceptable”.

       “Southwest does not condone employees sharing their personal political opinions while on the job serving our customers, and one employee’s individual perspective should not be interpreted as the viewpoint of Southwest and its collective 54,000 employees,” the statement released on Sunday read.

       According to an Associated Press reporter on board the flight from Houston to Albuquerque, the pilot’s use of the phrase drew audible gasps from some passengers.

       The airline company received flak on social media with growing demands for the pilot to be sacked for the incident.

       “The Southwest pilot who said, ‘Let’s go Brandon’ over the intercom, should be fired. Who agrees,” wrote actor Angela Belcamino on Twitter.

       Filmmaker Andy Ostroy wrote: “You better hope ‘Brandon’ is the name of all those new passengers you’ll be getting to replace all the libs now boycotting your airline.”

       During an event at Alabama’s Talladega Superspeedway in early October, a sports journalist misreported that a crowd shouting “F*** Joe Biden” was saying “Let’s go, Brandon”.

       An NBC Sports reporter was interviewing Brandon Brown, the winner of the race, when the crowd behind Brown started chanting “F*** Joe Biden”. The reporter suggested they were saying “Let’s go, Brandon” to cheer the driver.

       Since then, the chant has been uttered on the House floor by a Republican lawmaker and used frequently by Biden critics on social media.