Three of Queensland Rail's troubled new trains have been cleared for service, but it's still unclear how many will be on track in time for the Commonwealth Games in April.
Two of the New Generation Rollingstock trains will be deployed on Monday on the Gold Coast and Airport lines, while one will be held in reserve.
QR CEO Nick Easy said it was pleasing to finally have some of the $4.4 billion train fleet ready to roll out.
"There's been an enormous amount of work and a team effort to achieve these outcomes," Mr Easy told reporters on Wednesday.
"We've always said these trains will enter service by the end of the year, and we've been able to do that through the good work of all our teams."
Canadian manufacturer Bombardier has been building the trains at its Indian manufacturing plant after signing a contract with the previous Newman government in 2014.
But the Palaszczuk Labor government halted the contract in 2016 amid concerns over problems with the new trains, including line-of-sight issues, braking and disability access.
The three trains being rolled out represent a small fraction of the 75 ordered, and Mr Easy couldn't say exactly when the rest of the rolling stock would come online.
"There will be a progressive deployment of the balance of the trains until we have 75 trains that have completed their commissioning and assurance processes."
Mr Easy also couldn't confirm how many trains would be running during the Commonwealth Games in April, committing only to releasing the integrated transport plan for the event closer to the start date.
"The number of trains (ready for the Games) will be based on how many have passed their assurance tests, and we'll service the timetable we'll release in the new year."
There are currently 21 trains on the ground in Queensland, including the three which have already been cleared for service.
Deputy Premier and Transport Minister Jackie Trad said earlier this year she hoped to have 15 of the trains functional in time for the games, but later backed away from that figure.
Mr Easy explained that some of the trains would have to be modified in Australia because they had been manufactured before the issues were identified, while others would have their issues addressed at the point of manufacture.