On two occasions in the past, I was awarded bonuses from an Airline FF program due to labor disputes or other causes of cancelled flights. It is amusing that in both cases, I had not flown or tried to fly that airline during it's troubled period.

For America West, I was given 2500 bonus miles for being an active member of their FF program (though not during the labor dispute)

For American, as a Gold member, I was given 5 extra upgrade stickers during their most recent labour dispute.

This is a good reason to maintain all of your FF memberships, even if you have not flown that airline in a while.