"Ladies and gentlemen, this is your captain speaking," the pilot can be heard bellowing over the aircraft's loudspeaker.
"This is the most important announcement I have ever made. The federal mask mandate is over. Take off your masks if you choose.
"It is over … immediately."
The short clip was met with cheers and celebration as masks were removed, however the airline said it understood that some might have mixed feelings about the new ruling.
"It has been a long 24 months with nearly constant change," the airline's blog post read.
"I could not be prouder of our frontline employees who have handled every pivot focusing on safety and the care we're known for.
"We're also thankful for our guests who remained considerate, patient and stood by us throughout every twist and turn."
Some passengers vented their concern over the safety of travelling on board an aircraft without masks.
"My kid's on an Alaska flight as we speak," one wrote on Twitter.
"I am so p**sed off re airlines changing the rules mid-flight! Chose this travel date precisely because it was within the mask mandate period."
"I can't stop thinking about people who may have chosen to book and board this flight based on a personal risk assessment that involved everyone being masked," another added.
"And then, MIDFLIGHT, when it was physically impossible to leave, that element of their risk assessment was up-ended."
Another social media user, who was on board the flight, said while there was "some applause" many "kept it on".
"Please reinstate the mask mandate on your flights. If there is another airline that cares enough about my health that it requires masks be worn, I will be booking all my future flights with that airline."
United Airlines said that "effective immediately" masks will no longer be required on domestic flights, select international routes and within US airports.
"While this means our employees are no longer required to wear a mask — and no longer have to enforce a mask requirement for most of the flying public — they will be able to wear masks if they choose to do so, as the CDC continues to strongly recommend wearing a mask on public transport."
In Australia it is a requirement for passengers to wear masks on all domestic and international flights, as well as within airports.
In New Zealand, on Air NZ flights, all passengers are required to wear a face mask prior to reaching the boarding gate and on its flights.
