Add this code to categories, but do not include an extra newline before the <noinclude>, and you use the infobox name for sorting:

<noinclude>
[[Category:Infobox templates|Passengers]]
</noinclude>

Where Passengers may be, for example, used for "Infobox Passengers".

If you would like the infobox to force every page that includes it to be in a certain category, use the <includeonly> tags instead.