iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone 6+, released on 2018-03-29T17:12:21Z. The update package is 683.94 MB. This is a delta (partial) update that requires 11.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c3adea982a0b0b236e0138ff52f9119e97465ccd.zip.