Maverick Vinales topped Friday's second practice as the Moto3 riders learned their way around the Circuit of the Americas, with times tumbling dramatically relative to the morning session.
Seconds were shaved off the top lap time with all the riders setting new personal bests. Team Calvo KTM rider Vinales had set the pace early on and was almost 1.5 seconds faster after just three laps.
The Spaniard continued to set quick laps throughout, with his best of 2m 18.254 coming wit just over five minutes remaining. But he then pushed too hard and lost the front into turn one which finished his session.
The improved grip and track knowledge blew away Romano Fenati's fastest lap from the first practice, a 2m 22.098s.
The timesheets were once again lead by KTM machines with Estrella Galicia's Alex Rins second quickest. Early championship leader after victory in the opening round, Luis Salom, was third for Red Bull KTM Ajo.
Mahindra rider Miguel Oliveira once again had a promising start to the weekend after a competitive opener for the Indian team. The Portuguese rider pushed his Suter powered machinery up to fourth and was the first non-KTM rider listed.
Fenati was fastest Honda around the Austin track. The San Carlo Team Italia rider impressed after not really featuring in the Qatar race, salvaging one point from Losail, and finished practice fifth.
Jonas Folger's Mapfre Aspar Kalex KTM placed sixth while Isaac Vinales, cousin of Maverick, was seventh for the Bimbo-Ongetta-Centro Seta team.
Alex Marquez was eighth quickest for the Estrella Galicia team despite almost being hit by Eric Granado as he neared the line on his fastest lap.
A fast late-run for Danny Webb promoted him to ninth for Ambrogio Racing, the only team to run a Suter Honda this season.
The Honda-powered bikes generally appeared to benefit from the track layout being more varied after the fast, flowing opener in Qatar caused them to struggle.
The championship's only female participant, Ana Carrasco, was 16th at the end of practice for Team Calvo.
Red Bull Ajo rider Zulfahmi Khairuddin crashed towards the end, finishing down in 27th. The Malaysian rider already has a suspected wrist injury and was sent for tests after the Qatar round.
Brit John McPhee was in 30th on the timesheets for Caretta Technology – RTG.