Sony is pushing out the Android 4.4 KitKat update for the Xperia Z Ultra smartphone. Users in Hong Kong are reportedly getting the update first. THe update is only available as an Over-The-Air update so owners would not be flash it manually.
However, it is worth checking the settings for an update as it should be available there. It is a phased roll out and the update may not be available if you live in North America.
Expect the folks at xda developers to come up with a manual update package that will allow you to perform the update manually. HTC Butterfly S users have also started receiving the KitKat update that bumps Android version to 4.4.2.
It is a heavy 740 MB update so make sure you are on Wireless connection before you press the download button. Both updates are said to bring several changes to core functionality. Some cosmetic changes to the user interface can also be seen.