IAd banner on iPhone 6 wrong size?

Ok, so I'm updating the iOS app to take advantage of the larger iPhone 6 display, but iAd still shows iPhone 5s sized ads (both on the banner and when I select an ad).

There is an annoying blank space on each side of the banner and a full frame of white space around the view when choosing an ad.

My app has the correct iPhone 6 launch image and displays its native resolution (no scaling). Grateful if anyone can give me a pointer as to where I am going wrong.

The iAd frame is configured and sized with this code and located at the bottom of the screen:

[_UIiAd setFrame:(CGRectMake(0, screenHeight - 100, screenWidth, 50))];

      

        
        
        
      

    

It looks like this: