Two multi-car accident during mid-week qualifying for the Daytona 500 have seen seven drivers including Joey Logano and Brian Vickers resorting to back-up cars.
Jolyon Palmer topped the timesheets for Carlin in Friday morning practice at Monza for the ninth round of the 2013 GP2 Series and the final weekend of the championship in Europe.
Honours in the second 45-minute practice session at the Mid-Ohio Sports Car Course went to Penske's Will Power, who just edged Ganassi's Scott Dixon for the top spot in the afternoon.
Ganassi's Scott Dixon and Dario Franchitti made an early impact in proceedings at Mid-Ohio Sports Car Course in first practice on Friday ahead of this weekend's Honda Indy 200.
Romain Grosjean put Lotus at the top of the time sheets in Saturday morning practice ahead of Ferrari's Fernando Alonso, before a late yellow for a crash by Sergio Perez in the McLaren.