Fernando Alonso made his debut at Daytona International Speedway in the opening session of the pre-event 'Roar' test ahead of the 24 Hours on January 27-28.
Alonso, who already had experience of the United Autosports team's Ligier JSP217 from testing at the Aragon circuit in Spain in November, completed a five-lap run at the end of the 75-minute session after team-mates Phil Hanson and Lando Norris ran before him.
In just three flying laps Alonso worked down to a 1m39.604s compared to Norris's earlier mark of 1m38.170s, which put the #23 United Ligier sixth fastest overall.
Filipe Albuquerque set the pace driving the #5 Action Express Cadillac DPi, posting a best time of 1m37.266s.
That put him 0.262 seconds faster than the Wayne Taylor Racing Cadillac of Renger van der Zande.
Tristan Vautier, in the Spirit of Daytona entry, and Felipe de Oliveira, in the second Action Express car, completed a top-four lockout for Cadillac.
Colin Braun was the fastest non-Cadillac in fifth, 0.775s off the pace, in the CORE Autosport ORECA.
Juan Pablo Montoya was the best of the Penske Acura drivers in ninth place, 1.525s off the pace, with Ricky Taylor 14th in the sister car ahead of Paul di Resta's #32 United Ligier.
The Ganassi Ford team set the pace in GTLM. Richard Westbrook was fastest with a 1m44.095s, relegating team-mate Dirk Muller to second place.
Alessandro Pier Guidi was third in the Risi Competizione Ferrari 488 GTE ahead of Laurens Vanthoor's Porsche.
Rolf Ineichen was fastest in GTD in the Grasser Racing-run Lamborghini Huracan with a lap of 1m47.104s.