Historic 'Locomotive 3801' is the last streamlined steam locomotive in the state and arguably the country's most famous as it's the only engine to have visited all mainland states and territories.

To mark its long-awaited return, the 3801 is taking 1,500 passengers on sold-out trips between Sydney and Hurstville today and tomorrow.

In the next few months 3801 will also make trips to the Southern Highlands, Albury, Wagga Wagga, Junee, the Blue Mountains and towns in western and northern NSW.

Passengers can choose to travel in the open saloon or a private compartment car.

The train has always attracted major public enthusiasm, says Transport Heritage NSW CEO Andrew Moritz, and is the most asked about engine in their historical fleet.

"This engine has a following all of its own," he said.

"Being the 'Glamour express' it has always been a crowd favourite and attracts crowds wherever it goes."

In 2013, when Transport Heritage NSW was established, Premier Gladys Berejiklian said the organisation should prioritise returning the 3801 to service.

When Locomotive 3801 first launched in 1943, it immediately changed the image of NSW railways and epitomised the romance of the steam era.

The 38 class was fast, powerful and streamlined, and only the best crews were rostered to work the trains.

"It is that iconic epitome of steam, it represents the best technology of the day," Mr Moritz said.

"The streamlining makes it so representative of that Art Deco era, and the modernity that the railways were trying to project."

In 1964 the train made the fastest journey at the time between Sydney and Newcastle in just over two hours and in 1970 it became the first steam locomotive to cross the continent to Western Australia.

However, the 3801 was marred by tragedy in 1990 when an inter-city train hit the locomotive while traveling to Cowan, NSW, killing six people on the steam train.

The impact completely destroyed the last carriage of the 3801 and a nine-month ban was introduced on steam trains in NSW.

By 2007 the 3801 was withdrawn from heritage service due to major damage to its boiler.

A new boiler was ordered in 2010 from Germany but it had technical issues and eventually it was decided to repair the original boiler using the old-fashioned riveting technique.

The NSW government-funded $3.5 million overhaul of the 3801 was completed last year by a team of staff and volunteers, including some who worked on the train in its heyday.

"It's certainly become a much bigger job than was envisioned … it's been a labour of love," Mr Moritz said.

The restoration was carried out at the Chullora workshop in Sydney and has seen a new generation of steam specialists become qualified.

Story By | Paige Cockburn