The airline not only charged full fare for the cello, they created a separate account in the name of the cello, and credited it with the extra miles for ten(?) years before deciding to revoke not only the cello's miles but those of the musician.

It would seem reasonable that they revoke the extra miles for the cello, since they were clearly identifiable; but there doesn't seem to be much justification for taking those for the musician. A more reasonable response would have been invoking the "non-transferable" clause typically included and known by must requiring that only the cello could use the miles (with proper ID).

A post above cites the excellent response of an airline when:

"The clerk put a "Special Handling" tag on the case, and ..."

On a business trip, an item of equipment (aircraft part) needed to be returned to the factory, and "management" demanded that I "hand carry it" so they'd get it as quickly as possible. (Ground freight would have had it there in 3 days at the time, and I wasn't leaving by the time it would have arrived.) I had to purchase a "suitcase" large enough to hold it, but when I arrived at the airline they insisted it was "too heavy and besides it looked suspicious" so they marked it "special handling" and took it to do whatever special thing they insisted on doing.

Instead of arriving with me in Wichita, Kansas the next day (4 days after it could have been sent on its way by freight and a day after it would have been in Wichita ahead of me), it was located - ten days later - in Puerto Rico, and took a total of 48 days before it finally arrived in Wichita.

[They did reimburse me for the suitcase and I still use it occasionally. It's one of the nicer ones I have.]

John