I don’t see the benefit for a small Narrowbody what’s so ever today… With the increases of crew costs over the last 10 years, they see the value of spreading those increased costs over more seats in quite a bit of the domestic market.

The other segment of the market (premium), larger aircraft provides more floor space to offer more premium seats (domestic lie-flats, Higher number of FC seats, Premium Econ, more Econ+ seats, etc).

The primary reason why Delta took on the A220 to begin with is because Bombardier offered them at a steep discount to become a US launch customer. Just like how Delta acquired the 717s from Southwest after the Southwest/AirTran merger, very very cheap….

United isn’t going to get that kind of deal for the A220 from Airbus