This actually happened to me about 5 years ago. I was living in California at the time but I'm from South Carolina. I was going to Cherry Grove for my family reunion and I was actually waiting for my connecting flight in Dallas. Any ways they needed 2 seats and they kept asking at the gate for people to give up their seats and no one did.

So it was time to board the plane and they asked one more time over the intercom and no one did anything. I board and took my seat. Everyone had taken their seats then the flight attendant came over the intercom and asked one last time. At this time I figured why not I know I'll get a free flight, food, and board. I raised my hand along with another guy about my age.

We offloaded and our bags were pulled off. As we are heading to the checkin counter another attendant explained to us that the person they needed the seats for need immediate heart surgery and they had a transplant with them. Then she further explained that we could get flight vouchers worth $1000 or they could cut us a $1200 check and still give us food vouchers, book us on the next flight, and hotel vouchers for the night. Myself and the other guy glanced at each other and took the cash.

Funny thing I called to update my parents that I was going to be delayed by a day and my dad lost his shit. Even though we came out ahead on the cost of the flight.