Joined on the ground by the Queenstown and Southern Lakes Pipe Band, and from the air by a swooping Tiger Moth biplane, the Flyer chugged past tooting cars and waving onlookers, its passengers grinning with delight.
Queenstown resident Adrian Chisholm, who was riding the train with his 7-year-old grandson Eddie, said it was wonderful to be a part of the history.
"There's just something in our DNA; people just love steam trains."
The Flyer was first introduced in the late 1890s as a freight and passenger service between Kingston and the Main South Line in Gore, Simpson said.
"Arguably, this remaining 14km of the Kingston to Lumsden branch would be the most historically significant remaining part of a branch line left in New Zealand.
"The [line] opened in 1878 and it was to serve the Lakes district, connecting with the lake's steamers, which is very, very unique anywhere in the world."
The Flyer operated privately as a heritage steam train tourist attraction from 2003 until it was mothballed in late 2013, before being purchased by a group of Auckland-based investors in 2017.
Last July, the Flyer received consent to operate commercially, and yesterday marked the start of a public schedule which will see two services operate every Sunday until mid-December.
Simpson, who began working with the Flyer in 1987 as a fireman, said it was significant that both the train, and the vision to operate it commercially, had surpassed 50 years.
"It's been a turbulent 50 years, and it's been off and on in the last 20 odd years, but I think it's remarkable that it's still here and that it's still so hugely popular.
"It's absolutely great to just see so many people here today."