Characters
Define irony. Irony is a bunch of idiots singing a song on plane made famous by a band that died in a plane crash.
— Garland · Con Air

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker defines irony with a darkly comic example: a group of fools belting out a song on an aeroplane, when the band that made the song famous died in a plane crash. The humour comes from the grim mismatch between the singing and the song's history.
Context reviewed