Since iOS 7, the following methods have been introduced in UIViewController so you can control the status bar on a per-View Controller basis:

- (BOOL)prefersStatusBarHidden
- (UIStatusBarAnimation)preferredStatusBarUpdateAnimation
- (void)setNeedsStatusBarAppearanceUpdate
- (UIStatusBarStyle)preferredStatusBarStyle

-preferredStatusBarStyle is commonly used. Since there's a slight pause at the launch screen (showing Default.png and its variations), you'll want to make sure the status bar style used in the launch screen matches your app's initial screen's.

You can do this by editing your app's Info.plist, adding a property called Status bar style (UIStatusBarStyle) and instead of selecting a value from the drop down, type UIStatusBarStyleLightContent or UIStatusBarStyleDefault yourself.