Accidentally Deleted Macintosh HD

OK, thanks! Let's try this:

1. Start up from macOS Internet Recovery: Turn on your Mac, then immediately press and hold these three keys until you see a spinning globe: Option, Command (⌘) and R. 
2. From the utilities window, select Disk Utility and click Continue.
3. In Disk Utility, select View > Show All Devices.
4. Select APPLE SSD SM012... in the sidebar of Disk Utility. 
5. Click the Erase button in the toolbar, then enter the requested details:
   1. Name: Macintosh HD
   2. Format: APFS
   3. Scheme: GUID Partition Map
6. Click Erase, then click Done.
7. When done, quit Disk Utility to return to the utilities window, and select "Reinstall macOS".

If you have any questions, please let us know!

Jack

Hi there!

Try these steps:

1. Select "APPLE SSD SM012..." in the sidebar of Disk Utility.
2. Click the Erase button in the toolbar, then enter the requested details:
   1. Name: Macintosh HD
   2. Format: APFS
   3. Scheme: GUID Partition Map
3. Click Erase, then click Done.
4. When done, quit Disk Utility to return to the utilities window, and select "Reinstall macOS".

Let us know if these steps work!

Jack

Thanks! What year is your MacBook Air, and what version of macOS were you using before you erased Macintosh HD?

Jack

Hi! I am experiencing this exact problem. I used the steps you provided, I am connected to the internet. But MacOS High Sierra still won’t load. Help please 🙏🏽

Seems you deleted your entire macOS install; macOS itself, and all user files.

Here is how to: Erase and reinstall macOS - Apple Support

And then—If you have a Time Machine backup—here is how to: Recover all your files from a Time Machine backup - Apple Support

Are you connected to Wi-Fi? You can check by going to the Wi-Fi menu in the top right corner.

Jack