Chosen Solution
I have on my hands a 2013 A1466. The firmware is Mavericks era. I’ve got a nvme SSD that obviously can only be seen by a Mojave installer. I’ve tried the trick to install to an external, but same thing happens as with the internal, “an error occurred while verifying firmware” after first reboot. I’ve probably done several other things I cant think of right now, but I’ve researched this til my eyes crossed and cant find a solution that works for me. I just feel like I’m missing something here so hopefully a second mind can help here. Thanks.
Your MacBook Air offers a AHCI/PCIe 2.0 x4 interface (the Apple custom SSD’s where only AHCI/PCIe 2.0 x2. Here’s a good reference: The Ultimate Guide to Apple’s Proprietary SSDs Here’s a visual breakdown of the interface
As you didn’t tell us your exact M.2 SSD it may not be compatible and the adapter frame may not be the correct one or just bad. Frankly, while I fully understand the desire to use the cheaper M.2 blade SSD’s they are not 100 % compatible! There are issues with sleep mode and if you over fill your drive you can corrupt it. I do recommend sticking with a real Apple SSD or one of the better direct drop in SSD’s from OWC or Transcend.
