Cannot reinstall MacOS on macbook air early 2015, help!!!

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Cannot reinstall MacOS on macbook air early 2015, help!!!

Okay so ive basically deleted my macbook disk and tried to restart everything as I was trying to give it to someone, i followed this guide: What to do before you sell, give away, trade in or recycle your Mac – Apple Support (UK)

everything was going well, until the 'reinstall macOS' bit.

here is what i have tried:

1) trying command + R brings me to internet recovery where for some reason i am prompted to install mac os sierra which is an old version i suppose, nevertheless i do try installing it but as the progress bar finishes i get an error saying: an error occurred while preparing the installation please try again. i did try again multiple times to no avail.

2) option + command + R brings me to internet recovery again, i am once again prompted to reinstall macos sierra, and this time when the progress bar reaches the end i get this message: -5101F. I assume it meant i was not able to use internet recovery to download the macOS, so i trouble shooted it by using an ethernet cable and did confirm the ethernet cable worked by pinging apple on terminal but still, the mac installation failed yet again.

3) my last option was to use a bootable flash and install monterey as it is supported and i wouldnt want to be stuck with old sierra, figured its the reason i was having issues to begin with. so i followed this guide: Create a bootable installer for macOS – Apple Support (UK)

i used my new macbook air M1 to make the installer on a new flash and it was successfully installed, so i booted the 2015 mac using the flashdrive by holding the option key during start up. the USB does appear in boot picker, displaying the monterey installer, so im here like hooray this should deffo work.

i select it, apple logo shows, progress bar filling up... until it reaches the middle and....

showed a no entry symbol '🚫' with this text: support.apple.com/mac/startup

i am now lost. i have tried everything. i wish i never deleted this mac to begin with. it was working perfectly fine. PLEASE HELP

MacBook Air 13″, macOS 10.15

Posted on Sep 8, 2026 12:32 PM

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Answer 1

Top-ranking reply

HWTech

Community+ 2026

Level 9

76,356 points

Sep 9, 2026 9:11 AM in response to jooi23

Unfortunately Apple is very inconsistent with their various installers and is showing their disdain for the older online installers by not maintaining them.

With the Monterey USB installer, you must make sure to completely erase the internal SSD as GUID partition and APFS (top option) since the Monterey installer will not automatically convert the file system for you if it was using HFS+ (aka MacOS Extended). In fact, I think the installer may even allow the initial part of the install to work until the 2nd phase after the reboot which can make these things even more frustrating.

For the macOS 12.x Monterey installation, you will need to click "View" within Disk Utility and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility.

Consider yourself fortunate since you actually have access to another Mac that is compatible with an OS your 2015 laptop supports. So many people are not so lucky.

I am glad you found the Apple article for properly preparing a Mac for sale. Good job on that and everything else you have attempted. You have done well.

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Answer 2

Sep 8, 2026 4:10 PM in response to jooi23

If Recovery is trying to download Sierra, make sure that the drive is formatted as Mac OS Extended (journaled).

Sierra predates APFS, so if the drive is still formatted using APFS as the result of a previous Monterey installation, it is unlikely that things will work.

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Answer 3

Sep 8, 2026 10:24 PM in response to jooi23

jooi23 wrote:

1) trying command + R brings me to internet recovery where for some reason i am prompted to install mac os sierra which is an old version i suppose, nevertheless i do try installing it but as the progress bar finishes i get an error saying: an error occurred while preparing the installation please try again.

Try this:

https://mrmacintosh.com/fixed-an-error-occurred-while-preparing-the-installation-macos-sierra-recovery-error/

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