AT&T’s Microsoft Lumia 640 and Verizon's Lumia 735 smartphones are now receiving the Windows 10 Mobile update over the air (OTA).

Both AT&T and Verizon are rolling out the firmware in phases, meaning Lumia 640 and Lumia 735 users may have to wait for a couple of days before it hits all the handsets.

GSM Arena says AT&T's Lumia 640 owners can manually look for the software update by navigating to Upgrade Advisor app. Verizon's Lumia 735 owners, on the other hand, can go to Settings -> Update & Security -> Phone update -> Check for updates.

Verizon’s support page says, upon updating the Lumia 735 to Windows 10 Mobile, the device should show the following software version: “02171.00002.15194.03084.”

Microsoft released a YouTube video sometime toward the beginning of 2016 on how to upgrade to Windows 10 Mobile. According to the video, Lumia handsets running the Windows Phone 8.1 version of the operating system must download and install the Upgrade Advisor app, available in Windows Store. This app will check if the Lumia device is eligible for an upgrade.

Upon selecting the “Enable Windows 10 upgrade,” the app will verify if the device has enough disk space to handle the load from the upgrade. It will next ask the users to back up the device data with the help of SD cards, OneDrive cloud storage or saving it to any other preferred location. Following which, Lumia users can navigate to Settings -> Phone update to check for Windows 10 Mobile update.

(Credit: YouTube/Microsoft Lumia Support)

Speaking of eligibility, here is a list of Lumia and non-Lumia handsets earmarked to get the Windows 10 Mobile update: Lumia 1520, Lumia 930, Lumia 640, Lumia 640 XL, Lumia 730, Lumia 735, Lumia 830, Lumia 532, Lumia 535, Lumia 540, Lumia 635 1GB, Lumia 636 1GB, Lumia 638 1GB, Lumia 430, Lumia 435, BLU Win HD w510u, BLU Win HD LTE x150q and MCJ Madosma Q501.