My Mac air is displaying a question mark

Follow all four of the steps in If your Mac starts up to a question mark - Apple Support.

Flashing folder with a question mark is an error that may occurs when Mac cannot detect its boot directory. This usually happens when:

1. Mac cannot find the startup Disk.

2. MacOS is corrupt

However, you can try the below methods to fix the issue:

1. Boot your Mac into macOS Recovery Mode

2. Repair startup disk using disk utility

3. Reinstall macOS

Hope it helps!