Scott Redding, who hasn't qualified higher than tenth in Moto2 this year, sprung a surprise by leading Friday practice for the Indianapolis round.
The Englishman was a contender for most of the session, and retook the top spot for the Marc VDS (Suter) team by just 0.015sec from title leader Toni Elias on his very last lap.
Redding will now aim to continue his momentum and try to beat his best Moto2 finish to date, a fourth place at his home Silverstone round.
Second in the championship Andrea Iannone was third quickest for Speed Up, 0.125sec behind the Gresini Moriwaki of Elias, with the JiR run MotoBI of Simone Corsi just 0.157sec from Redding in fourth.
A notable performance came from wild-card Jason DiSalvo, who was tenth fastest at the end of his first ever Moto2 session on a GP Tech FTR.
DiSalvo, who split from the Triumph World Supersport team earlier in the season, was the top American.
Fellow wild-card Roger Lee Hayden, riding a Moriwaki run by American Honda and overseen by 500cc legend Kevin Schwantz, lost time due to an early technical problem - that left him stuck out on track with a locked rear wheel – on his way to claim 23rd, but was only 1.3sec from Redding.
Roger, younger brother of Nicky, usually races for Kawasaki in WSBK, but also finished eleventh in this year's US MotoGP at Laguna Seca as a stand-in for LCR Honda.
Team Scot, which began the season with Alex de Angelis and Niccolo Canepa, is not participating this weekend and faces an uncertain future.
de Angelis, due to the return to the Scot team after subbing for Hiroshi Aoyama in MotoGP, is trying to find an alternative ride for his home round at Misano next weekend.
Friday practice - Indianapolis:
1. Redding (Suter) 1m 46.728s
2. Elias (Moriwaki) +0.015s
3. Iannone (Speed Up) +0.140s
4. Corsi (Motobi) +0.157s
5. Simon (Suter) +0.327s
6. Bradl (Suter) +0.502s
7. Gadea (Pons Kalex) +0.589s
8. de Rosa (Tech 3) +0.654s
9. Talmacsi (Speed Up) +0.666s
10. DiSalvo (FTR) +0.707s