Championship leader Oscar Piastri went fastest Friday in a chaotic second practice session for the Singapore Grand Prix, punctuated by two crashes, red flags and a bizarre pit lane shunt.
Piastri sped round in 01:30.714sec, 0.132sec ahead of RB's Isack Hadjar with Max Verstappen's Red Bull third.
Fernando Alonso had been quickest in the first practice but showed it was no fluke by coming fourth in the second session under lights.
It was a welcome return to form for the Australian, who crashed last time out in Baku but avoided the chaos at the Marina Bay Circuit to top the time sheets.
It was first halted by George Russell crashing his Mercedes at turn 16.
When the cars got going again, Liam Lawson found the barriers near the end of the lap to bring out another red flag.
As cars vied for position in the pit lane for the next restart, Charles Leclerc's Ferrari was released into Lando Norris' McLaren, shunting it into the pit lane wall.
The McLaren was hastily pushed back into its box to fit a new front wing, and Norris was eventually fifth fastest with the second Aston of Lance Stroll sixth.
Esteban Ocon, Carlos Sainz, Leclerc and Lewis Hamilton rounded out the top 10.
"A bit of a weird one to be honest," said Russell of his crash.
"I'm not too sure what happened. I braked a bit earlier, went in a bit slower, but lost the rear.
"Thankfully, I went in front-end on and didn't do too much damage, but it was game over."
'Heat Hazard'
The race was on Thursday declared an official Formula 1 "Heat Hazard", invoking a new rule to help drivers beat the tropical heat in Singapore.
It means drivers will be able to wear newly developed cooling vests because ambient temperatures are expected to be 31 degrees Celsius or higher. Many drivers were seen trying out the vests and their associated maze of cooling tubes under their fireproof race suits.
The air temperature for both Friday sessions hovered around 28°C, cooler than usual in Singapore, but with humidity at a very uncomfortable 80 per cent.
McLaren are just 13 points from guaranteeing the constructors' championship in Singapore.
Norris, second in the championship, won in Singapore last year, and a repeat of that result would close the 25-point gap to his McLaren teammate.
Verstappen has won the last two races to edge into the title picture, 69 points behind the Australian with seven race weekends to go, but Verstappen has never won around the Marina Bay Circuit. He did come second last year, albeit 20 seconds adrift of race winner Norris.