That explains why I was asked to toss out my extras. By the way, this document says that Zippos are fine:

https://www.faa.gov/about/office_org/headquarters_offices/as...

That's a regulation I support, because unlike toothpaste it's a legit fire hazard. A broken lighter that shorts something out can get nasty quickly.

One lighter on a person means a problem will be relatively small and quickly noticed.

I carry 2-3 lighters in my backpack at any given time and fly regularly. Have never had to remove them or had them confiscated in the last 4 years.