Bruno Senna sped away from Toyota drivers Sebastien Buemi and Jose Maria Lopez to give Rebellion Racing a clear overall lead after one hour at Circuit of The Americas.
Senna controlled the start of the six-hour FIA World Endurance Championship race from pole position while Buemi moved past Lopez on the first lap to switch the Toyota TS050 Hybrids around.
However, no early challenge was provided to the No. 1 Rebellion R13 Gibson, in which Senna worked up an 18-second lead over Buemi heading into the first pit stops.
Lopez, meanwhile, had settled back into third by a similar margin but was approximately a minute ahead of the LMP2 class leader.
By the end of the first hour, Senna had just over 20 seconds in hand to Buemi.
In LMP2, Giedo van der Garde made a spirited charge to the head of the field after starting the Racing Team Nederland Oreca 07 Gibson from eighth on the nine-car grid.
The Dutchman made up a handful of positions in the opening laps before starting on a challenge for the podium positions.
After evading punishment for a clash into Turn 8 which turned Will Stevens’ Jackie Chan DC Racing Oreca around, Van der Garde overtook United Autosports’ Paul di Resta at the same spot to assume third.
The Nederland driver then went off-track to pass Andre Negrao in the esses, but overtook the Brazilian under braking shortly after handing the place back.
Van der Garde finally moved into the lead during the first round of pit stops, in which he jumped ahead of Nico Lapierre in the Cool Racing Oreca.
In GTE-Pro, Aston Martin settled into first and second courtesy of Alex Lynn’s overtake on Porsche driver Kevin Estre into Turn 2 on the opening lap.
This put Lynn behind his teammate Nicki Thiim, who started from pole, and the pair of Aston Martin Vantage GTEs controlled the pace of the opening hour.
Estre ran in third heading into the first round of pit stops at the start of Hour 2, ahead of James Calado in the No. 51 Ferrari 488 GTE Evo and Richard Lietz in the other Porsche.
Egidio Perfetti built up a substantial seven-second lead in the GTE-Am class for Porsche outfit Team Project 1, but the Norwegian driver’s advantage was eroded over the course of the stint by Paul Dalla Lana and Salih Yoluc in two battling Aston Martins.
Yoluc overtook Dalla Lana for second into Turn 12 at the end of the back straight, but the Canadian retrieved his lost position in the stadium section with a move that resulted in Yoluc spinning around.