As in Wednesday afternoon’s second session, the Alpine A480-Gibson grandfathered LMP1 sat at the head of the classification for the majority of the session on Thursday morning, only for the Glickenhaus 007 LMH to jump ahead towards the end.
After a quiet Wednesday for the Toyota GR010 HYBRIDs, they ran an early 1-2 with Brendon Hartley ahead of Jose Maria Lopez, but both failed to dip under the 1m50s barrier.
Nicolas Lapierre then went quickest with a 1m50.293s in the one-hour practice period, before working down to 1m49.664s that appeared to cement his position at the top of the times.
But with 20 minutes of the session to go, Lapierre's fellow Frenchman Olivier Pla then pipped him to the top spot with a time of 1m49.261s to end the session on top for Glickenhaus, 0.403s faster than the Alpine.
Third quickest was Filipe Albuquerque’s United Autosports LMP2 ORECA on 1m49.745s, just 0.081s off the Alpine’s pace.
The Portuguese driver's effort pushed his compatriot Antonio Felix da Costa down to fourth in his Jota LMP2 ORECA, with a lap of 1m49.980s.
The Toyotas ended the session in fifth and eighth, with the #7 car setting 1m50.169s, ahead of Paul di Resta’s 1m50.438s in the second United ORECA and AF Corse’s similar car.
The #91 Porsche 911 RSR-19 led the GTE Pro times early on, with Gianmaria Bruni setting the bar at 1m57.672s.
After a spell in the pits, Wednesday’s pacesetter Michael Christensen then beat team-mate Bruni’s time with a 1m57.448s lap just after the halfway point of the one-hour session in the #92 car.
Nick Tandy took third in the sole Chevrolet Corvette C8.R, just 0.021s off Bruni, with the GTE Am-leading Team Project 1 Porsche of Matteo Cairoli next up on 1m58.776s.
The AF Corse Ferrari 488 GTE Evos once again struggled, with James Calado unable to dip under 1m59.005s in fifth, and just over a tenth clear of Harry Tincknell in the best of the GTE Am Dempsey Proton Porsches.
Qualifying for Friday’s Sebring 1000 Miles begins at 7:00pm, local time.
Watch WEC 1000 Miles of Sebring qualifying and the race live on Motorsport.tv (geo-restrictions may apply).
