If you don't want to wait that long then you can use another way by installing the firmware manually using the written instructions on this post and at the end you will have a Nexus 9 Wi-Fi powered with LMY47X Android 5.1.1 firmware.
If you are ready then you can start it by firstly reading the preconditions points below.
- Just install this firmware on the Nexus 9 Wi-Fi tablet only, if you flash it on other devices then it won't work (Install LMY47X Android 5.1.1 Lollipop On Nexus 9 LTE).
- And your Nexus 9 should be using the Android 5.0.2 LRX22L. You can find it by going to Settings> About Device. So you can't flash it on either custom ROM or stock ROM that's not LRX22L.
- Do not forget to firstly enable your Nexus 9 Wi-Fi USB Debugging mode.
- And charge your battery until it's above %60.
- A Windows computer with a USB cable are ready to use.
How to flash Android 5.1.1 LMY47X Lollipop OTA Update for Nexus 9 Wi-Fi
- Download SDK adb tool.
- Then extract the file to your computer.
- Create an SDK folder in C: partition.
- When the folder is created, then open SDK manager.
- You will be told that there are some SDK packages and drivers that are need to be downloaded and installed. Therefore confirm the actions.
- When done installing the SDK Drivers then download the Google USB drivers, install it as well.
- Download LMY47X from here, then rename the file once it's downloaded, rename it to update.zip.
- Now put the update.zip file to the platform-tools folder (This folder can be found inside the SDK directory you previously setup).
- Now power off your Nexus 9 to enter the recovery mode.
- Then choose apply update from adb option.
- Connect your tablet to computer now.
- Back to the platform-tools folder now to launch the Command Prompt from you computer (Perform this inside the platform-tools folder).
- Enter adb devices within the command prompt to see whether your device's detected by your PC. If it's detected, proceed to the flashing process.
- Begin the installation by entering the adb sideload update.zip command in command prompt then confirm the process. Updating process will start. Just wait till finish guys.
- When the installation process is done just reboot your computer.