Joao Barbosa was fastest in the opening practice in Detroit for this weekend's Chevrolet Sports Car Classic.
Barbosa's best time in the 90-minute session on the 14-turn, 2.35-mile Raceway at Belle Isle was a 1:24.999, just reaching 1:24 territory.
The second Action Express Racing prototype driven by Eric Curran and Dane Cameron was second fastest in the session with a 1:25.041.
The rest of the top five was completed by the two other Corvette Daytona Prototypes entered this weekend as well as the Chip Ganassi Racing No. 01.
Renger van der Zande, driving in both United SportsCar and World Challenge at Detroit this weekend, was quickest in the first ever Prototype Challenge session at Belle Isle with a 1:27.668 in the No. 8 Starworks Motorsport FLM09. In GT Daytona, James Davison was quickest in the No. 007 TRG-AMR Aston Martin V12 Vantage GT3 with a 1:33.117.
During the session, two red flags came out - both to retrieve the No. 38 Performance Tech Motorsports Oreca FLM09 entry.
The second 90-minute practice session runs from 1:15 to 2:45 pm before qualifying for tomorrow's race this evening.