Ferrari's Michael Schumacher cruised to a dominant victory in the United States Grand Prix to breathe some life back into his world championship challenge.
US GRAND PRIX RESULT
1 M Schumacher (Ferrari)
2 F Massa (Ferrari)
3 G Fisichella (Renault)
4 J Trulli (Toyota)
5 F Alonso (Renault)
6 R Barrichello (Honda)
7 D Coulthard (Red Bull)
8 V Liuzzi (Toro Rosso)
Schumacher headed home team-mate Felipe Massa in a Ferrari one-two, with Renault's Giancarlo Fisichella third ahead of Jarno Trulli's Toyota.
Schumacher cut Fernando Alonso's lead in the championship to 19 points as the Renault driver struggled to fifth.
Jenson Button retired his Honda during an early safety-car period.
That was triggered by a multiple pile-up on the opening lap, in which seven cars were eliminated.
Schumacher lost the lead to Massa at the start, with Alonso jumping up to third from fifth, but behind them chaos erupted.
McLaren's Juan Pablo Montoya ran into the back of team-mate Kimi Raikkonen in the middle of the right-left chicane, knocking the Finn into Button's Honda.
Button's car then tagged the BMW Sauber of Nick Heidfeld, who was launched into a terrifying series of barrel rolls before coming to rest the right way up and uninjured.
Scott Speed's Toro Rosso was also caught up in the accident.
We know we had a very good car this weekend and to have Felipe alongside is a great thing
In a separate incident further down the field, Mark Webber's Williams was launched into the air in a tangle with Red Bull's Christian Klien and the Super Aguri of Franck Montagny, leaving all three out of the race.
Button's car was hit in the incident, but, more seriously, his engine overheated while running slowly behind the safety car, forcing the Englishman to retire.
It was the fourth consecutive race in which Button has failed to score points.
When racing resumed on the seventh lap, Massa held on to his lead, but Alonso, who had leapt from fifth to third at the start, began to come under pressure from Fisichella.
Schumacher bided his time until the first stops, when Massa ensured his team leader leapfrogged him with a slow in-lap.
"We definitely performed extremely well this weekend," said the 37-year-old German, who claimed his fifth win at the Indianapolis circuit.
"We know we had a very good car this weekend and to have Felipe alongside is a great thing.
"With Fernando taking fifth is good for the championship too. It couldn't be a better weekend."
Behind the Ferraris, Fisichella worked hard to pass the struggling Alonso, who finally succumbed to the inevitable on lap 14.
Fisichella edged closer to the Ferraris, but, once the first stops were over, the red cars moved clear despite apparently turning down their revs to conserve their engines.
Fisichella was almost as comfortable in third place, but Alonso had an unusually difficult race.
After winning six of the year's nine grands prix, never finishing lower than second, the Spaniard was left fighting a battle for fourth place with the Toyotas of Ralf Schumacher and Jarno Trulli.
Trulli took fourth with a most impressive drive after starting from the pit lane following a suspension failure in qualifying.
Toyota filled the Italian's car with plenty of fuel, enabling him to make only one pit stop.
That strategy, helped by the early safety car, had him up to sixth place before Alonso and Ralf Schumacher made their final pit stops, at which point Trulli leapfrogged them.
Alonso, struggling with his car's handling, also looked set to lose out to Ralf Schumacher.
But although the German passed Alonso at their second stops, demoting him to sixth place, Schumacher retired with wheel bearing failure in the closing stages.
Honda's Rubens Barrichello took sixth place after a low-key race, with Red Bull's David Coulthard seventh and Toro Rosso's Antonio Luizzi eighth.
United States Grand Prix final positions after 73 Laps:
1 Michael Schumacher (Ger) Ferrari 1hr 34mins 35.199secs
2 Felipe Massa (Brz) Ferrari 01:34:43.099
3 Giancarlo Fisichella (Ita) Renault 01:34:51.699
4 Jarno Trulli (Ita) Toyota 01:34:58.799
5 Fernando Alonso (Spa) Renault 01:35:03.599
6 Rubens Barrichello (Brz) Honda 01:35:11.699
7 David Coulthard (GB) Red Bull - Ferrari at 1 lap
8 Vitantonio Liuzzi (Ita) Toro Rosso - Cosworth at 1 lap
9 Nico Rosberg (Ger) Williams - Cosworth at 1 lap
Ralf Schumacher (Ger) Toyota 62 laps completed
Christijan Albers (Ned) Midland - Toyota 37 laps
Jacques Villeneuve (Can) BMW Sauber 23 laps
Tiago Monteiro (Por) Midland - Toyota 9 laps
Takuma Sato (Jpn) Super Aguri - Honda 6 laps
Jenson Button (GB) Honda 3 laps
Mark Webber (Aus) Williams 1 lap
Christian Klien (Aut) Red Bull 1 lap
Franck Montagny (Fra) Super Aguri - Honda 1 lap
Nick Heidfeld (Ger) BMW Sauber 1 lap
Juan Montoya (Col) McLaren - Mercedes 1 lap
Kimi Raikkonen (Fin) McLaren - Mercedes 1 lap
Scott Speed (USA) Scuderia Toro Rosso - Cosworth 1 lap