When Air Canada announced that it would drop Aeroplan and start a new frequent flyer program, Aimia (the company that owns the Aeroplan) saw its stock fall from about CAD$8.80 down to as low as about CAD$1.50 per share.
Activist shareholders replaced Aimia’s leadership, and they quickly announced aggressive plans to offer a competitive program that might continue to be attractive to customers. That gave the stock a bit of a bounce. But when Air Canada made their offer to buy the Aeroplan program from Aimia, Aimia’s stock shot up.