iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone 6+, released on 2018-03-29T17:12:19Z. The update package is 788.01 MB. This is a delta (partial) update that requires 11.0.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8a0f691ad758b6149c2b041ba735a2aa6cc91418.zip.