Filipe Albquerque led the first hour of the Daytona 24 Hours in the #5 Cadillac DPi entered by Action Express Racing.
Albuquerque moved into the lead during the opening round of prototype pit stops on 30 minutes, when his AXR crew performed a quicker stop than that of pole-sitter Renger van der Zande in the Wayne Taylor Racing Cadillac.
At the close of the first hour, Albuquerque held a five second advantage over Spirit of Daytona's Tristan Vautier, while Van der Zande lay back in fourth after the pit cycle.
Felipe Nasr ran third in the sister Action Express machine, as Cadillac asserted an early dominance on the IMSA Sportscar Championship season-opener.
Nasr was originally second after the stops, but Vautier muscled past the former Sauber F1 driver at turn one near the close of the hour.
Three-time Indianapolis 500 winner Helio Castroneves was the highest placed non-GM runner in fifth, driving the #7 Penske-Acura DPi.
Fernando Alonso had a trouble-free start to his first 24-hour race, with the United Autosports driver reaching as high as 11th from his grid position of 13th, before dropping to 14th in the busy prototype pack.
In GTLM, the pair of Ganassi-run Ford GTs dominated the opening stages, with Joey Hand and Richard Westbrook settling into a comfortable 15 second lead over Jan Magnussen's pole-sitting Corvette at the first round of stops.
However, a slow service for Westbrook's #67 Ford dropped that car out of the top five, leaving Hand on his own to maintain the lead ahead of Magnussen and the sister Corvette driven by Oliver Gavin.
Having started eighth, Alexander Sims entered the second hour in fifth position behind the wheel of the best-placed BMW M8.
GT Daytona pole-sitter Daniel Serra lost his advantage early on to fellow Ferrari driver Miguel Molina, who dictated the class pace for much of the first 60 minutes.
However, Land Motorsport Audi driver Jeffrey Schmidt was classified as the leader as Molina made his first visit to the pits shortly before the event's first chronological milestone.
