Applications built with Flex do not perform well on iOS when developed and packaged with Flex SDK 4.5.1 command-line tools.
Use the AIR 2.7 command line packager (adt) to package the application for deployment to iOS devices.
The Flex 4.5.1 SDK includes AIR 2.6. For the best performance on iOS, package your applications with AIR 2.7:
This issue only applies to the applications compiled with the SDK command-line tools. Flash Builder 4.5.1 includes the required components from AIR 2.7 to package iOS applications.