iOS 9.3 (build 13E233) is an official Apple over-the-air update for the iPhone 6+, released on 2016-03-21T18:56:28Z. The update package is 436.59 MB. This is a delta (partial) update that requires 9.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: afa907b8edbc0343b6fdc93529f39c9054211962.zip.