I was always told to call them "senior." I wouldn't use that casual term in a formal setting like a promotion or during a meeting. And I wouldn't use it with the person's name. It's of a nickname. For example, I'd call a person 'senior' but not 'Senior Snuffy.'

I'd say its similar to calling someone "el-tee." You'd never call a guy "El-tee LastName" but you sure call a lot of lieutenants "el-tee."

And I'm well aware it is technically against the AFI. But I've just lumped this under the nickname category (like el-tee, callsigns, etc).

I never cared about that stuff. I was called L-T plenty by enlisted types. As an Army warrant I was called "Chief" a lot too even though nothing in the ARs says that's appropriate. Just more queep to worry about while people are disregarding the rules that matter most.

Just a hint guys, from someone who's been retired for over seven years now (my how time flies!), in the old days everyone that was an NCO was called 'sergeant' until such time as they pinned on Chief, at which point they were called 'Chief.'

Anyone who was enlisted and not an NCO was called 'airman.'

It was simple and it worked...

My "older than you" statement. You could call an E-9 sergeant back in the day, it was in the reg. We would call real Chiefs, Chief, and E-9s sergeant.