Infinite Flight is an application that requires a lot of memory for textures, airplanes, scenery, etc... Some devices with low onboard memory can sometimes crash in situations where there are many applications running on the device or if they haven't been rebooted in a while.
The most affected devices are the iPod Touch 4th Gen, iPad1 and older devices which have very limited memory available for us to work with.
We advise users to restart their device periodically to reclaim memory used by other applications before starting to use Infinite Flight.
More recent devices like the iPhone 4S, 5, iPod Touch 5, iPad 2, 3, and 4 don't have such issues.