The model year of a MacBook Air is available at Apple menu > About This Mac.
A mid 2009 MacBook Air can be upgraded to El Capitan 10.11.6 but no later version. See: How to download and install macOS - Apple Support
A late 2010 through mid 2011 MacBook Air can be upgraded to High Sierra 10.13.6 but no later version. See: How to download and install macOS - Apple Support
A mid 2012 MacBook Air can be upgraded to Catalina 10.15.7 but no later. See: How to download and install macOS - Apple Support
A mid 2013 and early 2014 MacBook Air can be upgraded to the latest version of Big Sur macOS 11 but no later. See: How to download and install macOS - Apple Support
An early 2015 and a 2017 MacBook Air can be upgraded to the latest version of Monterey macOS 12 but no later. See: How to download and install macOS - Apple Support
A 2018 or later MacBook Air can be upgraded to the current version of Sonoma macOS 14. See: How to upgrade to macOS Sonoma - Apple Support