Danica Patrick tops opening IndyCar practice session at Las Vegas

The Andretti Autosport driver, who is making her final IndyCar appearance ahead of a full-time switch to NASCAR competition next year, was one of the last drivers out on-track.

However, her time of 24.735s with 10 minutes remaining proved enough to secure the top spot for the American.

With a few minutes to go she headed Ryan Hunter-Reay, Mike Conway and Marco Andretti in a top-four lock-out by the Andretti squad, however, a flurry of quick laps late on changed the order significantly.

Oriol Servia lapped 0.077s slower than Patrick to go second in his Newman/Haas Dallara, while Hunter-Reay and Conway rounded out the top five; the pair split by Chip Ganassi driver Scott Dixon.

Helio Castroneves was the top Penske driver in sixth, ahead of Andretti and his team-mate Ryan Briscoe.

Championship contenders Dario Franchitti (Ganassi) and Will Power (Penske) were only ninth and 14th while Ed Carpenter, who was quickest at the halfway point of the session, fell to 13th in his Sarah Fisher entry.

The session was put under full-course caution for over half an hour after fluid leaked out of the back of Ernesto Viso's KV car onto the track, and had to be cleaned up.

Pos  Driver               Team                     Time     Gap
 1.  Danica Patrick       Andretti                 24.734s
 2.  Oriol Servia         Newman/Haas              24.811s  + 0.077s
 3.  Ryan Hunter-Reay     Andretti                 24.827s  + 0.092s
 4.  Scott Dixon          Ganassi                  24.849s  + 0.114s
 5.  Mike Conway          Andretti                 24.863s  + 0.129s
 6.  Helio Castroneves    Penske                   24.868s  + 0.133s
 7.  Marco Andretti       Andretti                 24.869s  + 0.134s
 8.  Ryan Briscoe         Penske                   24.872s  + 0.137s
 9.  Dario Franchitti     Ganassi                  24.874s  + 0.139s
10.  Graham Rahal         Ganassi                  24.941s  + 0.205s
11.  Charlie Kimball      Ganassi                  24.942s  + 0.206s
12.  Tony Kanaan          KV                       24.966s  + 0.232s
13.  Ed Carpenter         Sarah Fisher             24.996s  + 0.261s
14.  Will Power           Penske                   25.013s  + 0.278s
15.  James Hinchcliffe    Newman/Haas              25.016s  + 0.281s
16.  Vitor Meira          AJ Foyt                  25.036s  + 0.301s
17.  Takuma Sato          KV                       25.042s  + 0.308s
18.  Simona de Silvestro  HVM                      25.055s  + 0.320s
19.  Pippa Mann           Rahal Letterman Lanigan  25.074s  + 0.340s
20.  Wade Cunningham      AFS/Sam Schmidt          25.343s  + 0.343s
21.  Paul Tracy           Dragon                   25.099s  + 0.364s
22.  Dan Wheldon          Bryan Herta/Sam Schmidt  25.101s  + 0.366s
23.  Alex Tagliani        Sam Schmidt              25.103s  + 0.368s
24.  JR Hildebrand        Panther                  25.110s  + 0.376s
25.  Ana Beatriz          Dreyer & Reinbold        25.120s  + 0.385s
26.  Buddy Rice           Panther                  25.151s  + 0.416s
27.  Tomas Scheckter      Sarah Fisher             25.167s  + 0.422s
28.  Davey Hamilton       Dreyer & Reinbold        25.199s  + 0.465s
29.  Sebastian Saavedra   Conquest                 25.204s  + 0.469s
30.  Townsend Bell        Dreyer & Reinbold        25.221s  + 0.486s
31.  Alex Lloyd           Dale Coyne               25.233s  + 0.498s
32.  EJ Viso              KV                       25.280s  + 0.548s
33.  James Jakes          Dale Coyne               25.316s  + 0.581s
34.  Jay Howard           Rahal Letterman Lanigan  25.327s  + 0.592s