The Airbus A220 has been a popular aircraft. Delta was able to buy a large number of them cheap before Airbus took over sales of the program from Bombardier. It has a low cost of operations and can fly surprisingly long distances. The wide fuselage makes it a passenger favorite for comfort because each seat gets extra width.
American Airlines doesn’t have an interest in the A220. Instead, American plans to pick up more Airbus A319s on the used market super cheap – a cost driven down, in part, by the growing popularity of the A220.