Nico Rosberg led a Mercedes one-two in opening practice for the Austrian Grand Prix, as both Sebastian Vettel and Fernando Alonso hit problems.
Rosberg set a best lap of 1:10.401 to outpace Mercedes teammate Lewis Hamilton by three tenths of a second.
Ferrari's Kimi Raikkonen finished in third over half a second behind, as teammate Vettel managed just four laps before stopping on track with a problem.
Valtteri Bottas was fourth fastest for Williams, with Felipe Nasr completing the top five in the Sauber.
Alonso's weekend started on the back foot as he was seen coasting back into the pits with an apparent problem following his installation lap.
The McLaren driver, also facing a penalty for using his fifth engine of the season, did not return to the track until there were 17 minutes left on the clock.
Alonso then covered just 10 laps before returning to the pits and calling it a day before the session had finished.
Last year's pole-setter Felipe Massa, ninth in the session, set the early pace for Williams under a cloudy sky, with teammate Bottas relegating him to second nearly 20 minutes into the session with a lap of 1:14.160.
Williams' domination did not last long, however, as Rosberg went nearly 1.5 seconds quicker than Bottas just a minute later. Hamilton also set a fast lap to move into P2, two tenths behind his teammate.
Rosberg lost first place momentarily to Raikkonen, to quickly regained the top spot with another flyer, setting a new benchmark of 1:11.389.
Seconds later, Vettel's running came to a sudden stop when he was forced to park his Ferrari after reporting to have lost drive.
The German had failed to set a time up to that point, and although his car was recovered and taken back to the pits, he was unable to return to the track.
After several minutes of quietness, Hamilton improved his time but not position with some 38 minutes left on the clock, although the Briton's run included two offs at Turn 1 and Turn 8.
|6||Daniil Kvyat||Red Bull||1:11.642||1.241||31|
|7||Daniel Ricciardo||Red Bull||1:11.724||1.323||29|
|8||Max Verstappen||Toro Rosso||1:11.825||1.424||38|
|10||Sergio Perez||Force India||1:11.905||1.504||37|
|11||Carlos Sainz||Toro Rosso||1:11.948||1.547||32|
|13||Nico Hulkenberg||Force India||1:12.031||1.630||36|