During the recent volcanic eruption on the Big Island of Hawaii, some passengers were treated to views of the eruption and lava flows by Hawaiian Airlines for free.
On the occasions when flights from Hilo left early (which occurs quite often here), the aircraft was flown at 2000-ft SE along the Puna coast and then turned around to let passengers on the other side of the plane see the view. The whole detour would add about 10 minutes to a 45-minute trip so was only done if they wouldn't arrive late. I don't know if the extra fuel costs got added on later to other flights, but I thought it was a nice touch. I'm sure the pilots enjoyed it as well. It was also quite unusual for us "locals". The helicopter tours went into full overdrive during this time (I lived under the flight path) but on the odd occasion, I would be driving home to see an HA 717 fly low just off the coast - definitely not something we see every day!