Air Tags

I have tried logging into iCloud using my account on my wife's iPhone and none of the Air Tags show up on the Find My app on her iPhone. Does this mean that the Air Tags are only visible on the iPhone that they were originally registered on. If I were to lose my iPhone how would we see the Air Tags?. Last year Lufthansa lost both our bags and we didn't get them back for a fortnight and we are trying to avoid this happening again.

Thanks