Mike Conway set the pace in an incident-filled Free Practice 1 ahead of the Six Hours of Silverstone which saw two red flag periods.
He posted a best time of 1:39.916 in the No. 7 Toyota TS050 Hybrid, going 0.275 seconds quicker than Sebastien Buemi in the No. 8 car.
Rebellion Racing classified third and fourth as the best-placed non-hybrids, with Gustavo Menezes quicker than his teammates with a time 1.027 seconds off the overall pace.
The SMP Racing BR Engineering BR1 AERs were next, ahead of DragonSpeed and ByKolles Racing Team.
TDS Racing led the way in LMP2 with an early flier set by Loic Duval putting the No. 28 Oreca 07 Gibson seven-tenths ahead of the No. 38 Jackie Chan DC Racing car.
Ford Chip Ganassi Racing had a 1-2 placement in GTE-Pro with Stefan Muecke improving on co-driver Olivier Pla’s time late in the session to keep the No. 66 Ford GT on top in class.
The Porsche 911 RSRs were the next quickest cars, separated in third and fifth by the No. 51 AF Corse Ferrari 488 GTE.
Matteo Cairoli took Dempsey Proton Racing to the top of GTE-Am, ahead of the similar Gulf Racing Porsche of Ben Barker.
The session was extended by 15 minutes following the first red flag period, called for Bruno Senna going off track at Copse, which halted the session for 30 minutes.
WEC debutant Rene Binder stopped on the Wellington Straight in the ByKolles ENSO CLM P1/01 NISMO later on, calling the red flag for a further 11 minutes.
Free Practice 2 will get underway at 4:25 p.m. local time.
RESULTS: Free Practice 1