More than 10,000 people lined the East Perth Terminal on February 23, 1970 to witness the historic completion of the first "unbroken" transcontinental train trip from Sydney, spanning a colossal 4352 kilometres.

Previously, traversing the nation by rail took many stops and train changes, and was an exhausting undertaking with little comfort.

These days, the 65 hour journey is a luxurious and seamless experience, with the ditching of "cattle class" - which involved non-reclining seats - in mid-2016.

Gold class is now the minimum standard, with bunk-style sleeping in the twin cabins, while double beds and a "chairman's carriage" that accommodates up to eight guests are available in platinum class, which debuted in 2008.

The most special guests on the 50th anniversary trip are Jeanne and Derek Kell, who met on the Indian Pacific 47 years ago while he was on holiday from England and she was Sydney-based.

"We didn't know each other - we were just nodding acquaintances on the train. Jeanne and I were in opposite single compartments and then at Broken Hill, Jeanne seemed to have disappeared," Mr Kell told AAP.

"I thought she'd got off ... but we saw each other again at Cook and eventually I plucked up the courage and spoke to her when we stopped at Rawlinna.

"After that, we were talking to each other all the time.

"We realised were were made for each other."

Mr Kell returned to the UK and they corresponded by letter for eight months then got engaged over the phone.

Luke Walker, chief operating officer of Indian Pacific operator Journey Beyond, said the company planned to expand the train from 29 carriages to 35.

Mr Walker said slow train travel had undergone a renaissance, with the average travelling speed a leisurely 85km/h.

"We're finding that's right on-trend with people, taking a bit of time to experience the food, the wine, the culture, the languages and the traditional owners," he told reporters on Sunday.

Transport Minister Rita Saffioti said the WA government was looking into extending the service from East Perth train station to Fremantle to make the journey a truly ocean-to-ocean experience and boost the port city's tourism.

"We're undertaking some preliminary work ... our discussions have begun," she said.

On the Perth to Sydney journey, the first stop is Kalgoorlie where the usual excursion to the massive Super Pit gold mine will be followed with a special concert to mark the 50th anniversary.

The final stop in the Blue Mountains will depend on clearing a landslide across the track caused by much-needed recent rain following devastating bushfires.

Australian Associated Press