Defending world champion Fabio Quartararo was fastest in Saturday practice for the Grand Prix of the Americas as six-time MotoGP title winner Marc Marquez was fourth on the time charts.
Both men ensured direct passage to the second qualifying run later Saturday.
Current championship leader Aleix Espargaro, who claimed his maiden MotoP victory in Argentina last weekend, was only 11th fastest on his Aprilia and must take his chances in the opening qualifying period.
Quartararo clocked 2min 02.361sec on his factory Yamaha with the Ducati pair of Enea Bastianini, the winner in Qatar last month, and Jack Miller filling out the top three.
Marquez, who has won seven of the eight races held at the Texas circuit, was just 0.129sec behind the French pace-setter.
Marquez is returning to the championship having had to sit out Argentina due to double vision suffered in a violent high-side crash in Indonesia last month.
Johann Zarco, Francesco Bagnaia, Pol Espargaro, Joan Mir, Takaaki Nakagami and Luca Marini made up the top 10.
Alex Rins, the Suzuki rider who broke Marquez's run of success at Austin by winning the 2019 race, is also in the opening qualifier as is Maverick Vinales of Aprilia and Jorge Martin who crashed out on his Ducati 14 minutes from the end of the session.