Having only just released the Android 5.0.2 update for the Google Nexus 9, the company didn't waste much time updating their flagship tablet to Android 5.1 Lollipop, their newest version of their mobile operating system.
Google has sent out a tweet, announcing that the Android 5.1 update is now being rolled out for the Nexus 9, but failed to specify which which version of the tablet will be receiving the update. Hopefully the update is rolling out to both Wi-Fi only and the LTE versions will be updated at the same time.
Although Google has already updated most of its Nexus tablet line-up to Android 5.1 Lollipop, the Nexus 9 has stayed behind on Android 5.0.1 Lollipop. After releasing the Android 5.0.2 update, which seemingly was a prerequisite for Android 5.1, Google didn't take long to push out the newest update.
Google has also started rolling out the Android 5.1.1 factory images to all other Nexus tablets, so it is safe to assume that it's the same update that the Nexus 9 is now set to receive.
Android 5.1 Lollipop is a minor update to Google's mobile platform, but it does bring several underlying improvements. Google's focus with the new update has been to eradicate all the bugs that have been left behind by Android 5.0, although it does enable users to join Wi-Fi networks and pair Bluetooth devices directly from the Quick Settings menu.
Google has yet to release the official Android 5.1 factory images for the Nexus 9, meaning that you'll have to wait for the OTA update to reach your device, at least for now.
source - Google | AndroidAuthority