'/execute unless' command fails on ALL targets even if only one meets the 'unless' criteria

repeating command block: /execute as @e[tag=spell] at @s unless block ~ ~ ~ air run kill @s

the command should succeed if the 'spell' entity is NOT in an air block

When any 'spell' entity fails to execute (due to the unless command) all others also fail, no matter whether they are in an air block or not.