Macbook Air failing to boot up properly

This morning my wife’s Macbook Air (maybe 5-6 years old) booted to a failed installation screen. It is running High Sierra with the most recent update. Booting with the Option key showed it was trying to boot from an installation partition. Selecting the hard drive allowed it to boot normally. I will attempt to sort this out when I get home tonight so would appreciate any suggestions. I suspect I will end up doing a complete reinstall but maybe this is a simple fix.

All help much appreciated.

Steve

Try an SMC Reset: How to reset the SMC of your Mac - Apple Support

Thanks Gehenna but I just got home and my wife has done a clean install of High Sierra so I guess I’ll never know what the problem was. Probably a not totally perfect update to 10.13.5 a couple of weeks ago.

Sweet, make an SMC Reset your first port of call when any weirdness like that happens again.

I’ve had this with my Mum’s 2010 White MacBook - a couple of times over the last year or so it has booted to the recovery partition for no particular reason. It’s running Sierra and has an SSD and 4GB of ram upgrade.