Reigning Moto3 world champion Maverick Vinales has taken his first Moto2 victory at only his second attempt after passing Dominique Aegerter for the lead with six laps to go in Austin.

Vinales then bolted, while Qatar winner Esteve Rabat lost time getting around Aegerter for second place. Xavier Simeon, who had been leading until a sideways braking moment with seven to go, fell while trying to take third from Aegerter on the penultimate lap.

The start was delayed due to spots of rain, but the race remained classified as 'dry' with slick tyres used by all.

A first turn incident triggered by home rookie Josh Herrin resulted in Mattia Pasini, Sam Lowes, Jordi Torres and Franco Morbidelli also ending up on the ground.

Herrin's Caterham team-mate Johann Zarco then wiped out Julian Simon from the lead group several laps later...

1. Maverick Vi?ales SPA Pons HP 40 (Kalex) 41m 31.520s
2. Esteve Rabat SPA Marc VDS Racing Team (Kalex) 41m 35.529s
3. Dominique Aegerter SWI Technomag carXpert (Suter) 41m 38.843s
4. Mika Kallio FIN Marc VDS Racing Team (Kalex) 41m 40.110s
5. Simone Corsi ITA NGM Forward Racing (Forward KLX) 41m 41.454s
6. Thomas Luthi SWI Interwetten Paddock Moto2 (Suter) 41m 48.507s
7. Anthony West AUS QMMF Racing Team (Speed Up) 41m 49.081s
8. Alex De Angelis RSM Tasca Racing Moto2 (Suter) 41m 50.468s
9. Marcel Schrotter GER Tech 3 (Tech 3) 41m 51.240s
10. Ricard Cardus SPA Tech 3 (Tech 3) 41m 56.072s
11. Takaaki Nakagami JPN IDEMITSU Honda Team Asia (Kalex) 41m 59.983s
12. Mattia Pasini ITA NGM Forward Racing (Forward KLX) 42m 15.475s
13. Randy Krummenache SWI IodaRacing Project (Suter) 42m 15.864s
14. Sandro Cortese GER Dynavolt Intact GP (Kalex) 42m 17.186s
15. Hafizh Syahrin MAL Petronas Raceline Malaysia (Kalex) 42m 20.811s
16. Sam Lowes GBR Speed Up (Speed Up) 42m 22.674s
17. Franco Morbidelli ITA Italtrans Racing Team (Kalex) 42m 22.851s
18. Azlan Shah MAL IDEMITSU Honda Team Asia (Kalex) 42m 23.203s
19. Axel Pons SPA AGR Team (Kalex) 42m 23.633s
20. Tetsuta Nagashima JPN Teluru Team JiR Webike (TSR) 42m 33.623s
21. Roman Ramos SPA QMMF Racing Team (Speed Up) 42m 33.866s
22. Thitipong Warokorn THA APH PTT The Pizza SAG (Kalex) 42m 35.015s
23. Julian Simon SPA Italtrans Racing Team (Kalex) 42m 36.464s
24. Robin Mulhauser SWI Technomag carXpert (Suter) 42m 41.461s
25. Gino Rea GBR AGT REA Racing (Suter) 42m 51.850s
26. Jordi Torres SPA Mapfre Aspar Team Moto2 (Suter) 43m 5.301s