I asked for a Drambuie (with one ice cube) when flying Singapore Air a few years back. Cue look of horror of my face as the flight attendant is about to pour it into a plastic cup (this was back in my college days when I didn't buy bottles of the stuff very often .. just a tad expensive in NZ).

Anyway, asked if I could get it in a glass. "No problem, sir.". She arrived back from the front of the plane moments later with a nice tumbler, popped in a cube of ice, and filled it to the top ... I didn't need a re-fill ^

Some things have to be in glass, no matter where you're sitting.