Two airborne IndyCar crashes in a week have raised safety concerns ahead of the Indianapolis 500, later this month.
Chevrolet drivers Helio Castroneves and Josef Newgarden both walked away from separate accidents in which their cars flipped over - leading to worries about new vehicle aerodynamic kits.
"It's definitely concerning," said CFH Racing owner Ed Carpenter. "We haven't had cars doing that ever in my career."
Englishwoman Pippa Mann also spun off into a wall in practice on Wednesday.
|BBC Sport's Andrew Benson|
|"The concern is that if it's happened twice, it can happen again. And it could suggest there might be an inherent instability problem in those circumstances with some of the latest aerodynamic packages used by IndyCars on so-called super-speedways, such as Indianapolis, where average lap speeds are nudging 230mph.|
|"IndyCar racing is likely to take establishing what has happened extremely seriously. It is not unknown for a set of rules to create a fundamental instability in the cars that race under them.|
|"In endurance racing a decade and more ago, a characteristic of the cars' aerodynamic designs led to several take-off accidents. One eventually cost the life of former Ferrari F1 driver Michele Alboreto."|
"We're still learning, to be honest," Castroneves said. "There are so many little details with the new aero kit that we're just starting now to go through that phase. My team-mates are going through that phase as well and we're just starting.
Three-time Indy 500 winner Castroneves lost control of his car before it hit the perimeter wall and went airborne on Wednesday.
The following day, Newgarden lost control of his CFH Racing car going into the first turn at Indianapolis Motor Speedway before the car flipped and rested on its side after hitting into the wall.
"I'm still trying to gather my thoughts from it," said Newgarden. "It definitely surprised me."
Neither driver was seriously injured.
However, Mann, 31, said her crash was nothing to do with changes to the car.
She said: "My accident would have happened with those circumstances with last year's aero kit, with the 2011 car. It was just one of those things."
Practice will continue on Friday in the build-up to the 500-mile race on 24 May.