The body of the three-time world champion, clad in a race suit, was laid out in a closed casket topped with his race helmet in the centre of the cathedral from 08:00 to 12:00 local time followed by a public mass and a private funeral.
It was the first time a sports star has been laid out in the cathedral, an honour previously accorded to prominent personalities such the archbishop of Vienna, Cardinal Franz Koenig, and the former crown prince of the Austrian-Hungarian empire, Otto von Habsburg.
Austrian media report that Hamilton will attend, together with other Formula One heavyweights such as Bernie Ecclestone and Mercedes chief Toto Wolff, to mourn Lauda, who won the drivers’ world championship in 1975 and 1977 with Ferrari and in 1984 with McLaren.
Even after retiring as a race driver, the Austrian remained a fixture on the circuit. Most recently, as non-executive chairman at Mercedes F1 since 2012, he was instrumental in bringing in Hamilton, sparking a run of success for the team.
The Briton won the Monaco Grand Prix Sunday, which he described as the “hardest race I think I’ve ever had”.
“That was for you, Niki. Your fighting spirit was right there with me every step of the way. I know you are looking down and taking your hat off to us. I miss you, we truly miss you and I hope we did you proud today, legend,” Hamilton posted on Twitter after the race.
In all, some 300 VIP guests are expected to attend the mass Wednesday, with 800 further seats and 3,000 standing places open to the general public.
Former F1 drivers Gerhard Berger and Alain Prost are expected to speak, as is Austrian President Alexander Van der Bellen and former California governor and actor Arnold Schwarzenegger.
During the mass, songs including “Amazing Grace”, “Fast Car” by Tracy Chapman, John Lennon’s “Imagine” and “Hero” by Family Of The Year will be played.
Lauda, who had struggled with health issues since miraculously surviving a 1976 race crash that saw his car engulfed in flames, died at the University Hospital Zurich in Switzerland, nine months after he underwent a lung transplant.
Lauda, recognised by his trademark red cap hiding scars from the accident at the Nuerburgring in Germany, also underwent kidney transplants.
One of the kidneys was donated by Birgit Wetzinger, a former flight attendant, whom the racer and businessman later married and with whom he had twins, a boy and a girl, in 2009.
Lauda also had three other sons from previous relationships.
Besides racing, Lauda’s second passion was aviation. He founded and then sold several airlines with his latest, Laudamotion, going to Ryanair in 2018.
It is not clear where Lauda will be laid to rest. The family reportedly has turned down an offer by the city of Vienna to receive a “grave of honour” in the city’s vast Central Cemetery.