Queen Elizabeth II dies — follow the latest news as the world mourns
Flightradar24 said a total of 4.79 million people watched the flight live online, with another 250,000 people watching on its YouTube channel.
The flight-tracking website said an unprecedented six million people tried to follow the flight within the first minute of the Boeing C17A Globemaster turning on its transponder at Edinburgh's airport, affecting the stability of the platform.
"Seventy years after her first flight as queen aboard the BOAC Argonaut 'Atalanta', Queen Elizabeth II's final flight is the most tracked flight in Flightradar24 history," the site's spokesman said.
Queen Elizabeth II, Britain's longest-reigning monarch died in Balmoral, Scotland, on September 8. Her funeral will take place on Monday.
Rehearsals for procession of Queen Elizabeth's coffin in London - in pictures
The late monarch is lying in state in London's Westminster Hall, where mourners can visit to pay their last respects.
Flightradar24 said the flight was more than twice the previous record of 2.2 million, when US House Speaker Nancy Pelosi flew on a controversial visit to Taiwan in August.