World Superbike Championship leader Carlos Checa sent out a warning signal to his rivals during first free practice at Miller Motorsports Park as he topped the session by six tenths of a second, despite missing a large portion of it.
An eventful session for the Spaniard, who was denied a double win around the American venue last season by technical issues, Checa was hit by another mechanical problem during the opening ten minutes of the session, but was soon back out and lapping quickly on the Althea Ducati.
Surging to the top of the timesheets with 25 minutes remaining, Checa's session swiftly came to an end when he came off the 1098R, possibly caused by another technical issue.
Even so, his time of 1min 48.914secs was still well clear of Leon Camier in second position, the Briton getting an uncustomary good start to a weekend by out-pacing his Aprilia team-mate Max Biaggi in third place.
Jakub Smrz moved up to fourth place late on aboard the Effenbert Liberty Ducati, while the following Michel Fabrizio, Jonathan Rea, Troy Corser, Tom Sykes and Eugene Laverty ensured all seven manufacturers were represented inside the top ten.
Elsewhere, Leon Haslam could only manage 14th best on the factory BMW, two spots behind Ayrton Badovini on the satellite Italia S1000RR. Badovini's team-mate, the returning James Toseland, was 19th quickest.