why can't I update my ipad air 2?

These models are all able to be updated to the current version, iPadOS 16.6

iPad Pro

iPad Air 3rd generation and later

iPad (5th generation and later)

iPad mini (5th generation and later)

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support

Hello ~ The iPad Air 2 can’t be updated to iOS 16.

~Katana-San~