A passenger train filled with students collided with a freight train on February 28, 2023, near the Tempi gorge in central Greece.
Two years later, the safety gaps that caused the crash have not been filled, an inquiry found on Thursday.
A separate judicial investigation remains unfinished and no one has been convicted in the accident.
That exasperates many in Greece, where mistrust of government is rife following a 2009-18 debt crisis in which millions lost out on wages and pensions, and public services suffered from underfunding.
All international and domestic flights were grounded as air traffic controllers joined seafarers, train drivers, doctors, lawyers and teachers in a 24-hour general strike to pay tribute to the victims of the crash.
Across the country, businesses were shut, theatres cancelled performances and by early morning, thousands began to gather in the capital's central Syntagma Square under the watch of police in riot gear. A sign read: "Government of murderers".
The names of those killed were spray-painted in red on the ground in front of the parliament building.
In the city's suburbs, groups of all ages made their way downtown with placards reading "I have no oxygen", a slogan of the protests echoing a woman's last words in a call to emergency services. Many pupils went to class dressed in black, a symbol of mourning.
In a survey carried out this week by Pulse pollsters, 82 per cent of Greeks asked said the train disaster was "one of the most" or "the most" important issue in the country and 66 per cent said they were dissatisfied with the investigations into the accident.
Prime Minister Kyriakos Mitsotakis' centre-right government, which won re-election after the crash in 2023, has faced repeated criticism by relatives of the victims for failing to initiate a parliamentary inquiry into political responsibility.
The government denies wrongdoing and says it is up to the judiciary to investigate the accident.
In a Facebook post on Friday, Mitsotakis said his government would work to modernise the railway network and make it safer.
"That night, we saw the ugliest face of the country in the national mirror," he wrote of the night of the crash.
"Fatal human errors met with chronic state inadequacies."
Opposition parties have accused the government of covering up evidence and urged it to step down.
Next week, parliament is expected to debate whether to set up a committee to investigate possible political responsibility in the disaster.
