I was upgrading my dad's 2013 Air yesterday and it got into a time-sapping install loop where it couldn't install 10.13 once I'd wiped the drive and reformatted to APFS. I had to enter internet recovery, wipe and reformat to HFS+, then restart the 10.13 install without wiping and reformatting.
I thought APFS was mandatory for all boot SSDs but nothing else. P'raps not.
I was upgrading my dad's 2013 Air yesterday and it got into a time-sapping install loop where it couldn't install 10.13 once I'd wiped the drive and reformatted to APFS. I had to enter internet recovery, wipe and reformat to HFS+, then restart the 10.13 install without wiping and reformatting.
I thought APFS was mandatory for all boot SSDs but nothing else. P'raps not.