It's Toprak Razgatlioglu who ends FP1 fastest in Aragon.
Nicolo Bulega finishes second ahead of Alvaro Bautista in third.
Vierge, Sam Lowes, and Iannone complete the top-six, while van der Mark, Gerloff, Alex Lowes, and Rea round out the top-10.
A late crash for van der Mark at the final corner after the flag was out. He's slid a long way, but no replays showing clearly what happened.
Late improvement from Gerloff, he's up to seventh on the Kawasaki which - predictably - lost a lot in the final split.
Improvement for Bautista - he's up to third on a 1:49.3.
Razgatlioglu now heading out for his second run. 5 minutes on the clock.
Finally a 1:48 for Bulega, but a 48.920 still leaves him 0.535s behind Razgatlioglu.
Bulega on track for his second run of the session. No improvements yet but running consistently in the low-1:49s.
1:48.385 now for Razgatlioglu and he's 0.6s clear of Bulega now. A late start for the BMW rider but it has been quite the impact almost immediately.
Razgatlioglu fastest now and by quite a distance - 1:48.719 sees him ahead of Bulega by 0.321s and he's the first rider in the 1:48s.
Razgatlioglu a little late to the party in terms of timed laps, but goes up to second with his first lap - 1:49.120.
Bulega now to the top on a 1:49.413, and then goes faster again with a 49.040 - he leads by 0.385s now over Lowes.
Bulega now to within a couple of tenths of Lowes, and Bautista up to third.
Yari Montella has suffered a bike problem. He's 16th at the moment but that could be his session over. He's over at turn 13/14 in the bus stop section before the back straight.
Times scrolling here, Iannone had been to the top, but now it's Sam Lowes fastest again on a 1:49.425.
Bulega second now from Bassani, Rea, and Bautista in the top-five.
Sam Lowes with the early pace here in FP1, 1:50.961.
Pit lane is open in Aragon and we are underway for 45 minutes of FP1.
With three rounds to go, 36 points separate Danilo Petrucci, Andrea Locatelli, and Alvaro Bautista in the fight for third in the standings.
Bautista won here twice last year, but hasn't won since, while neither Petrucci nor Locatelli have Aragon podiums to their name in WorldSBK.
Toprak Razgatlioglu has never won at Aragon in WorldSBK, but comes here having won the last 12 races in a row.
Nicolo Bulega is also winless at Aragon, but the long corners of MotorLand suit the characteristics of the Panigale V4 R and also of Bulega's smooth style.
The Italian was unfortunate in Race 1 last year, retiring on the warm-up lap, but was third in both Sunday races.
You feel victories here will be essential for Bulega to have any realistic hope of beating Razgatlioglu to the title by the time we get to Jerez next month.
Welcome to live coverage of today's World Superbike practices from Aragon. FP1 will be coming up in just over 10 minutes at 10:35 local time.