It’s a fools errand for airlines like American or United to offer a lowest common denominator product. When a business produces a commodity product, the lowest cost producer wins. Spirit is at a great advantage because American and United will always have higher costs.
Given their cost structure legacy airlines need to earn a revenue premium. And customers are already beginning to make buying decisions on more than schedule and price a trend that is only going to become more pronounced as passengers are presented with information during the booking process on what to expect from their flights like seat power and high speed internet.