Ayrton Senna's crash and death
Ayrton Senna was killed on 1 May, 1994 after his Williams FW16 crashed into a concrete barrier while he led the 1994 San Marino Grand Prix.
Senna's passing came one day after Austrian driver Roland Ratzenberger lost his life when he crashed his Simtek car into the wall during qualifying, and two days after Jordan's Rubens Barrichello clipped a kerb and crashed into the barriers at 95G, which resulted in a broken nose and sprained wrist.
Senna and Ratzenberger's deaths marked the first time a fatal incident had occurred at an F1 event since Riccardo Paletti's passing at the 1982 Canadian GP. This prompted the implementation of new safety measures in F1 and at circuits, as well as the re-establishment of the Grand Prix Drivers' Association.
Senna's move from McLaren to Williams
While Williams were seen as contenders for the title, Senna noted in pre-season testing that he hadn't come to terms with the car yet.
Those issues carried over to the start of the season, as the Brazilian had his worst F1 start after failing to finish or score points at the opening two races, despite taking pole position in both.
As a result, Senna headed into the San Marino GP trailing Benetton's Michael Schumacher by 20 points.
The fateful San Marino GP weekend begins
The weekend got off to bad start when Barrichello crashed at the Variante Bassa china at 225km/h.
Senna got out of his Williams car and went to the scene of the accident, where FIA doctor Sid Watkins performed emergency work on Barrichello, whose tongue blocked his airway.
Barrichello eventually regained consciousness, having suffered a broken nose and sprained wrist, though he didn't take part in the rest of the race weekend.
Things got even worse on Saturday. During the second qualifying session in the afternoon, Ratzenberger crashed into the concrete wall on the outside of the Villeneuve curve at 314 km/h due to a suspected front wing failure. Senna got inside a course car and arrived on scene as Ratzenberger was taken into an ambulance.
From there, news broke that Ratzenberger had passed away, with Senna and neurosurgeon Sid Watkins leaving the Medical Centre together. Watkins told Senna he didn't have to race again and suggested he withdraw from racing and go fishing with him, with the Brazilian stating he couldn't stop.
Senna opted not to take part in the rest of the qualifying session and did not attend the post-qualifying press conference.
On Sunday morning, Senna was fastest in the warm-up session by 0.9s and later took part in a drivers' briefing with Gerhard Berger. Having been involved in a row with race officials for commandeering a course car to visit the scene of Ratzenberger's crash, Senna asked the Austrian to raise concerns over the presence of the pace car during the formation lap, as its only purpose was to promote the latest Porsche 911.
Senna then met with fellow drivers in an attempt to re-establish the Grand Prix Drivers' Association in order to improve safety in F1. He offered to take the role of leader, starting at the following race in Monaco.
Senna's fatal crash at Tamburello
The black cloud that hung over the Autodromo Enzo e Dino Ferrari that weekend continued once the lights turned green on race day. Pedro Lamy and JJ Lehto were involved in a serious crash when the Lotus driver slammed into the back of the stalled Benetton.
Debris flew everywhere and caused minor injuries to a police officer and eight spectators. The collision resulted in the Safety Car being deployed, driven by German Formula 3 driver Max Angelelli.
The Safety Car remained on track for five laps, but Senna had pulled up alongside the Opel Vectra, which was a family sedan, to gesture to the driver to speed up.
The race resumed on Lap 6, with Senna leading and Schumacher behind him in second. The next lap saw Senna's Williams leave the track in a straight line at Tamburello and crash into a section of unprotected concrete barrier.
Telemetry showed that Senna entered the corner at 309km/h, braked hard, downshifted twice and then impacted the wall at 211km/h.
The impact tore off the front-right wheel and nose cone before coming to a halt, with Senna motionless in the car.
The front-right wheel had shot up on impact and entered the cockpit, thereby striking the front-right area of Senna's helmet. The impact itself shoved the Brazilian's head back against the headrest while causing skull fractures.
A piece of suspension attached to the wheel also partially penetrated his helmet and caused head trauma, while a jagged piece of the upright assembly penetrated the helmet visor just above his right eye.
Any of the three injures may have led to his death.
Crash aftermath and announcement
Immediately after the crash, Senna made a slight movement with his head, raising hopes regarding his injuries.
Fire marshals arrived on the scene first, though they had to wait for medical personnel, who came minutes after. Television coverage from an overhead helicopter was broadcast around the world as Senna received medical treatment.
An emergent tracheotomy was performed by neurosurgeon Sid Watkins to establish a secure airway. Watkins also cleared the respiratory passages, stemmed the blood flow, replaced lost blood and immobilised the cervical area.
While Senna's car was eventually lifted onto a truck and returned to the pit lane, the Brazilian was transported to Maggiore Hospital, where doctors rushed him into intensive care.
Senna's heart stopped beating shortly after 15:00 local time and doctors restarted it, but the decision was made not to restart it after another stop at 18:37.
Doctor Maria Teresa Fiandri, the head physician of the emergency department, had been watching the race from home but arrived at the hospital at the same time as Senna. Fiandri became responsible for medical updates to the media and public and, at about 19:00, announced that Senna had passed away 20 minutes earlier.
It was later revealed that a furled Austrian flag was found in Senna's car, as he had intended to honour Ratzenberger after the race.
Senna's funeral in Brazil
Senna's death was considered a national tragedy in his native Brazil, with the government declaring three days of mourning.
The funeral took place on 5 May, 1994 and was broadcast live on Brazilian television. An estimated 3 million people took to the streets of Sao Paulo while many prominent motor racing figures attended the funeral.
The Tokyo headquarters of Honda, where McLaren-Honda cars were displayed after every race, was overwhelmed by floral tributes, despite the fact Senna no longer raced for the team.
Safety improvements in F1
At the following race in Monaco, retired F1 World Champion Niki Lauda announced the reformation of the Grand Prix Drivers' Association (GPDA).
The Austrian was elected as one of the representatives along with Schumacher, Berger and Martin Brundle.
Immediate changes were made for the Spanish GP and Canadian GP, while more followed including improved crash barriers, redesigned tracks and tyre barriers, higher safety standards, higher sills on the driver cockpit and a limit on 3-litre engines.