MacBook Air model A1370 not booting.

Evadfa Said:

"MacBook Air model A1370 not booting.: [...]it then says 'Updating Boot Support Partitions For The Volume As Required'. I’ve been watching it and that’s as far as it has made it. Not sure what to do now."

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👍 Excellent job troubleshooting.

If a restart does not work...

Reinstall the macOS:

Nothing would be deleted. It's just that items that have become corrupted or deleted, would be replaced or reinstalled back to where they should be. Go Here: How to reinstall macOS from macOS Recovery - Apple Support

Evadfa Said:

"MacBook Air model A1370 not booting.: I have the MacBook Air laptop. When I turn it on, the Apple logo appears and then the spinning wheel appears below it. Nothing else happens. Can anyone tell me what I can do or is this thing giving me the wheel of death thank you"

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About Twirling Ball:

When this occurs, your Mac's lost of processes are occurring in the background. So, perform the following...

Troubleshooting Lagging Mac:

I. Getting to Boot:

A. Try Safe Mode:

In Safe Mode, login items do not run, and corrupt system files(i.e. caches) are intentionally reset as a way to fix issues

1. Boot: in to Safe Mode: [Hold Down: shift key upon boot].
2. Log in: as same user
3. Wait: 30 seconds
4. Restart; your Mac
5. Log in: as same user

B. See if your Hard drive is Failing:

What to Try:

• Verify your Drive: Repair your Disk in Disk Utility - Apple Support
• Go Here: If your Mac Starts Up to an Apple Logo or Progress Bar - Apple Support
• Perform the following in Recovery Mode:

1. Boot: into Recovery Mode. Go Here:  How to Use Safe Mode on your Mac- Apple Support
2. Select: Disk Utility
3. Select: the Drive
4. Click: First Aid button

II.Once logged in...

A. Remove Login Items:

While in Safe Mode, remove all of your Login Items, and then restart the Mac.  Go Here: Change Users & Groups Login Items Preferences on Mac - Apple Support

B. RAM Consumption being the Culprit::

As for the beachball, it is telling you that an application or file or sorts is at work. Likely. this app is consuming lost of RAM. So, view the Activity Monitor, seeing what is consuming the most of it, and close whatever it may be. More on Activity Monitor: Activity Monitor User Guide - Apple Support.  See my reply to this post: News Streaming Sites Consuming Lots of RAM ( >4GB) - User Tip