The App Store only shows updates for the OS you are using at the moment, in your case Yosemite 10.10.5.
If you want to go to another newer OS that is called an upgrade. This can be done through the App Store using the following link.
What you're encountering is not related to the pre-existing version, but likely that your MacBook Air is not supported for Yosemite at all. Apple lists the Late 2008 model as the earliest MacBook Air which can run Yosemite. Dec 07, 2017 Actually my Mac is running Yosemite MacBook Air (13 inches, early 2014) Intel Core i5 1.4 GHz 4 GB 1600 MHz DDR3 Intel HD Graphics 5000 1536 MB I don't know if I should update any of these, I did not try any operating system. Version 10.11: El Captain Version 10.12: Sierra Version 10.13. Buy Apple Laptop MacBook Air MJVM2LL/A 5th Generation Intel Core i5 1.6 GHz 4 GB Memory 128 GB SSD Intel HD Graphics 6000 11.6' Mac OS X v10.10 Yosemite with fast shipping and top-rated customer service.Once you know, you Newegg!
High Sierra is the last/ newest OS your Mac can use. Scroll down to Section 4 and click on Get macOS High Sierra.
Make a full back up of your Mac before upgrading.
Os X Yosemite For Macbook Air 10
Check to see with the developers of any third party apps you use that there are updates available so they will continue to work in the new OS. Another thing you need to check is if any printers/ scanners etc you use have updated drivers and software so they too can continue to function in the new OS.
Os X Yosemite For Macbook Air Pro
Feb 3, 2019 11:15 PM