iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone 6+, released on 2018-03-29T17:12:20Z. The update package is 690.24 MB. This is a delta (partial) update that requires 11.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 2dce7de5c4f02f4d94cbfaa4d2acc6b871d22f47.zip.