MacBook Air 2015 won't boot, Disk Utility fails in recovery

You have the following choices:

• Install macOS to an external USB3 drive so you can boot this laptop from an external drive so you can try accessing the data on the internal SSD
• Put the broken laptop into Target Disk Mode so you can connect it to another Mac using a Thunderbolt cable to attempt to access the data on the broken laptop
• Remove the internal Apple OEM SSD and put it into an OWC Encore Enclosure so you can connect it to another Mac
• If you are familiar with the command line, then you can try to access & copy the data to external media
• See if a local Apple tech can access the data....Apple won't help to recover data since they expect the user to have backups. An Apple Authorized Service Provider may offer a service to recover data.
• Contact a professional data recovery service

I hope this incident has shown you how important backups are. People should always have frequent & regular backups of their computer and all external media (including the cloud) which contains important & unique data. There are a lot more new ways to permanently lose access to the data stored on the internal SSD of the recent Macs due to all the hardware, software, and security changes.

Melati1 wrote:

How can I make a usb bootable? I tried downloading macOS onto the usb in recovery mode but it didn’t work… my neighbour was trying to help me but he couldn’t just ‚download‘ macOS in the App Store as he doesn’t want to install the version I am using..

Here is an Apple article with instructions for creating a bootable macOS USB installer:

Create a bootable installer for macOS - Apple Support

Melati1 wrote:

Follow up: how can I connect two macs with thunderbolt if my MacBook doesn’t have thunderbolt?

If you have a 2016+ Mac with USB-C ports, then those USB-C ports usually support both Thunderbolt & USB protocols (some Mac desktops may have USB-C ports that only support USB only, check the ports for an identifier mark & the product specifications).

If your other Mac has USB-C ports, then you will need to use a USB-C to Thunderbolt2 adapter & Thunderbolt2 cable.