Budapest - Australian Daniel Ricciardo reminded Formula One's title contenders that he and Red Bull remain a force to reckon with after posting the fastest time in opening Hungarian Grand Prix practice on Friday.
Fourth in the championship standings but 60 points behind Ferrari's leader Sebastian Vettel at the mid-point in the season, the Perth driver clocked a best time of one minute 18.486 seconds.
Ferrari's Kimi Raikkonen was second fastest, 0.234 slower on the same super-soft tyres, at a circuit that ranks almost as a home venue for the Finn.
Mercedes' Lewis Hamilton, a point behind Vettel in the standings and chasing a record sixth Hungarian victory on Sunday, made it three teams in the top three with a lap 0.372 off Ricciardo's pace.
Vettel was more than a second slower than Ricciardo in sixth place on a warm but cloudy morning at the Hungaroring outside Budapest.
"Struggling a lot with oversteer and rear tyres didn't seem to be ready," the German said over the team radio.
Ricciardo's Dutch team-mate Max Verstappen was fourth with Mercedes' Valtteri Bottas fifth.
Red Bull have brought important aerodynamic updates to Hungary, a track that has suited them in the past, and are hoping to be closer to Ferrari and champions Mercedes.
"It's all aero stuff, but hopefully it all works together and gives us the laptime we desire. It's a combination of things," Ricciardo, winner in Hungary in 2014, had told reporters on Thursday.
"On the windtunnel it looks like it should help downforce and hopefully that gives us the lap time."
There were encouraging signs at struggling former champions McLaren, who had Fernando Alonso seventh and Belgian team mate Stoffel Vandoorne eighth at the slowest permanent track on the calendar.
Renault's luckless Briton Jolyon Palmer brought out red flags at the end of the session when he smashed his front wing on a kerb, leaving debris over the track and puncturing the car's right front tyre.
Ferrari reserve driver Antonio Giovinazzi, having a Friday morning run in the Haas in place of Denmark's Kevin Magnussen, had earlier brought the session to a halt when he hit the barriers.
FIRST PRACTICE RESULTS
1. Daniel Ricciardo (Australia) Red Bull - TAG Heuer - 1:18.486
2. Kimi Raikkonen (Finland) Ferrari - 1:18.720
3. Lewis Hamilton (Britain) Mercedes - 1:18.858
4. Max Verstappen (Netherlands) Red Bull - TAG Heuer - 1:19.162
5. Valtteri Bottas (Finland) Mercedes - 1:19.248
6. Sebastian Vettel (Germany) Ferrari - 1:19.563
7. Fernando Alonso (Spain) McLaren - 1:19.987
8. Stoffel Vandoorne (Belgium) McLaren - 1:20.005
9. Nico Huelkenberg (Germany) Renault - 1:20.150
10. Jolyon Palmer (Britain) Renault - 1:20.461
11. Felipe Massa (Brazil) Williams-Mercedes - 1:20.540
12. Sergio Perez (Mexico) Force India - Mercedes - 1:20.574
13. Daniil Kvyat (Russia) Toro Rosso - Renault - 1:20.780
14. Carlos Sainz Jr (Spain) Toro Rosso - Renault - 1:20.917
15. Lance Stroll (Canada) Williams-Mercedes - 1:20.974
16. Romain Grosjean (France) Haas - Ferrari - 1:21.313
17. Alfonso Celis (Mexico) Force India - Mercedes - 1:21.602
18. Marcus Ericsson (Sweden) Sauber - Ferrari - 1:21.785
19. Antonio Giovinazzi (Italy) Haas - Ferrari - 1:22.251
20. Pascal Wehrlein (Germany) Sauber - Ferrari - 1:22.490