Miguel Oliveira headed the Moto2 timesheets on a tight Friday in Texas after topping both practice sessions on his Red Bull Ajo KTM.
Oliveira was the early pacesetter in the opening intermediate class session of the Americas Grand Prix weekend, the Portuguese rider deposing Joan Mir with a 2:14.630s.
Alex Marquez held top spot briefly in FP1 on his Marc VDS Kalex, though Oliveira soon struck back with a succession of quick laps, the best of which a 2:12.260s midway through the session.
Oliveira maintained first position, bettering his prior effort with a 2:12.104s in the closing stages, though his margin was only a slender 0.041 seconds over Marquez.
The opening session proved disastrous for both of the season's race winners, with Mattia Pasini restricted in track time due to a gearbox issue, while Francesco Bagnaia took a knock from his bike when he crashed at Turn 3 in the final minutes.
Both brushed off their woes for the afternoon session, with Pasini running inside the top five for much of the 45 minutes, while Bagnaia took things more steadily in 12th.
Oliveira picked up where he left off in FP1, posting the best time of the day in the Moto2 class with a 2:11.656s just minutes into the session, before improving to a 2:11.104s.
The Portuguese rider was unable to better that laptime and no one was able to surpass it, though CGBM's Sam Lowes came close on his final flying lap with a 2:11.125s.
Marc VDS' Marquez held onto third on the combined times ahead of the second Ajo bike of Brad Binder, while rookie Joan Mir on the sister Marc VDS machine rounded out the top five.
Isaac Vinales guided his SAG Kalex to sixth in the closing stages of FP2, edging ahead of Iker Lecuona on the second CGBM KTM by just 0.008 seconds. Pasini and Jorge Navarro completed the top 10.