iOS 9.3 (build 13E5214d) is an official Apple over-the-air update for the iPhone 6s+, released on 2016-02-22T17:47:47Z. The update package is 165.24 MB. This is a delta (partial) update that requires 9.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 330ca7ccba934bfdb91c4f1cd01bffcd5b3a9abf.zip.