Which MBA model do you have? To find the complete model information select About This Mac from the Apple menu. You can create a snapshot of the dialog as follows:
How to take a screenshot on your Mac
Capture, Save or Record Screenshots in Mac OS X - Help Desk Geek
OS X Screen Capture Shortcuts
(⌘⬆︎3) Command-Shift-3 Capture the screen to a file
(⌘⬆︎⌃3) Command-Shift-Control-3 Capture the screen to the Clipboard
(⌘⬆︎4) Command-Shift-4 Capture a selection to a file
(⌘⬆︎⌃4) Command-Shift-Control-4 Capture a selection to the Clipboard
(⌘⬆︎5) Command-Shift-5 Invoke new screen grabber
You can then post the image in the forum's message editor.
What version of macOS are you trying to install? If your MBA is from Late-2011 or later, then it supports Internet Recovery:
Internet/Network Recovery of El Capitan or Later on a Clean Disk
If possible back up your files before proceeding.
- Restart the computer. Immediately, at or before the chime, hold down the (Command-Option-Shift-R) keys until a globe appears.
- The Utility Menu will appear in from 5-20 minutes. Be patient.
- Select Disk Utility and click on the Continue button.
- When Disk Utility loads select the target drive (out-dented entry w/type and size) from the side list.
- Click on the Erase button in Disk Utility's toolbar. A panel will drop down.
- Set the partition scheme to GUID.
- Set the Format type to APFS (SSDs, only if installing Mojave or Catalina ) or Mac OS Extended, (Journaled.)
- Click on the Apply button, then click on the Done button when it activates.
- Quit Disk Utility and return to the Utility Menu.
- Select Install OS X and click on the Continue button.
This should install the original version of macOS when it was factory new. If you are selling or giving away your computer, then be sure you followed all the instructions in Factory reset of your Mac - Apple Support before erasing the drive. After the installation finishes shut down the computer. Do not proceed with the Startup Assistant.
