Kimi Raikkonen beat Lewis Hamilton to the fastest time in opening practice for the Monaco Grand Prix, in a session interrupted by a long red flag to attend to a loose drain cover.
The 16-minute stoppage began just before the one-hour mark, after officials noticed the problem with the drain cover on the hill out of Sainte Devote. It was repaired in time for the session to resume for the final 21 minutes.
Hamilton had been quickest for McLaren prior to the interruption, having lapped in 1:17.078 early on. He then improved the benchmark to 1:16.216 shortly after the session was restarted
But with nine minutes to go, he was usurped by Raikkonen, as the Ferrari driver produced a 1:15.948 to beat Hamilton by 0.268 seconds. Those times would stand as neither driver managed a clear lap on their last runs.
Heikki Kovalainen beat Raikkonen's initial sector times in the second McLaren, but could not sustain the advantage around the final part of the lap and ended up third.
Raikkonen's teammate Felipe Massa completed the top four in the second Ferrari, with Williams' Nico Rosberg beating BMW's Robert Kubica to fifth place in the closing seconds.
Double Monaco winner Fernando Alonso took seventh, as his Renault teammate Nelson Piquet continued to struggle. The rookie was only 18th fastest in the session, 1.5 seconds slower than Alonso.
Behind Honda's Rubens Barrichello and Red Bull's Mark Webber, Monaco specialist Giancarlo Fisichella achieved an excellent 10th place for Force India, while the new Toro Rosso showed early promise as Sebastien Bourdais claimed 13th place.
Jarno Trulli and Nick Heidfeld were the only drivers to fall foul of the barriers in the opening session. A brush with the wall on the approach to the tunnel broke the Toyota's suspension, and Trulli had to park on the exit of the chicane.
Nick Heidfeld came to a halt at Casino Square around the same time after apparently damaging the rear of his BMW - the German quizzically examing the back of the car after exiting the cockpit - while a throttle problem on his Red Bull prevented David Coulthard from completing a flying lap, as his car came to a halt between the chicane and Tabac.
Pos Driver Team Time Laps
1. Raikkonen Ferrari (B) 1:15.948 26
2. Hamilton McLaren-Mercedes (B) 1:16.216 + 0.268 27
3. Kovalainen McLaren-Mercedes (B) 1:16.248 + 0.300 28
4. Massa Ferrari (B) 1:16.292 + 0.344 26
5. Rosberg Williams-Toyota (B) 1:16.653 + 0.705 27
6. Kubica BMW Sauber (B) 1:16.834 + 0.886 23
7. Alonso Renault (B) 1:17.498 + 1.550 25
8. Barrichello Honda (B) 1:17.511 + 1.563 26
9. Webber Red Bull-Renault (B) 1:17.798 + 1.850 23
10. Fisichella Force India-Ferrari (B) 1:17.835 + 1.887 26
11. Glock Toyota (B) 1:17.942 + 1.994 26
12. Button Honda (B) 1:18.153 + 2.205 26
13. Bourdais Toro Rosso-Ferrari (B) 1:18.245 + 2.297 30
14. Heidfeld BMW Sauber (B) 1:18.263 + 2.315 13
15. Nakajima Williams-Toyota (B) 1:18.274 + 2.326 28
16. Trulli Toyota (B) 1:18.360 + 2.412 16
17. Sutil Force India-Ferrari (B) 1:18.360 + 2.412 25
18. Piquet Renault (B) 1:18.955 + 3.007 32
19. Vettel Toro Rosso-Ferrari (B) 1:19.176 + 3.228 35
20. Coulthard Red Bull-Renault (B) No time 3
All Timing Unofficial