Yes, once, as a DM. From Y to F on SIN to HKG.

There was another DM near me who was doing a DYKWIA act about a seat that didn't recline and demanding a better one, and the ISM decided that she had had enough of his whinging, so she invited me to take a new seat (J was full, so it was in F) and told the DYKWIA that he had a new seat, which was my old Y seat.

I enjoyed the Krug