Turn off split screen IPad Air 2

To close split view in Safari : About Multitasking on your iPhone, iPad, and iPod touch - Apple Support

With iOS 10, you can use Split View in Safari to see two tabs at the same time when your iPad is in landscape mode. Just touch and hold and tap Open Split View. If you have an external keyboard connected, press Command-N to open Split View.

Tap the search bar and search or enter a website name. If you already have a tab open, you can drag the tab left or right in the Split View.

To leave Split View, touch and hold and tap Merge All Tabs. You can also tap to close tabs individually and leave Split View.