After “Des Moines…?” my immediate thought was to work through whether this was a display of their real capabilities, or a warning shot? But this doesn’t signal they are capable of more. A DDoS attack against a public-facing website is something any modestly savvy teenager could launch. It doesn’t serve as a message that ‘we can reach your systems, and next time will be worse.’
Instead it’s more moderately annoying for the individual airports involved at best, the kind of attack someone would launch who wanted to say that an attack was made without actually doing one.