Why would United make that change? It's all about selling a higher percentage of the higher fare premium seats on a plane and having fewer unsold seats that are then filled with frequent fliers upgrading to business class.
"The nature of the airline business shouldn't be about giving away the product," noted Harteveldt. "The nature of the business needs to be about selling the product to as many people who will pay for it. That is a tough challenge but one I think the airlines are trying to respond to by right-sizing the size of the premium cabin."
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Business class fares vary depending on the route, time of day and demand in a particular market. Still, most industry analysts estimate business class fares on transcontinental flights are approximately 50 percent higher than coach fares on the same route. According to masFlight, and aviation consulting firm, roughly 11 percent of the seats on transcontinental flights are business class. That percentage has held steady in recent years, though it could be increasing as more airlines upgrade their service between the coasts. JetBlue is the latest to say it will offer premium service on its transcontinental flights, starting next year.
Targeting Corporate Customers
While United is the first airline to turn to lie-flat business class seats, its two primary competitors are not far behind. At the end of March Delta will start flying planes with lie-flat seats and American will do the same later this year. The carriers are upgrading their transcontinental flights because that's where they are in a heated battle for corporate customers.
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"There are a couple of groups that represent a disproportionately large number of premium business travelers. Financial services, consultants, independent business executives and a few other industries like entertainment," explained Harteveldt. "Those industries pay for premium cabin seats. That is the battle.
That is where the profit is and that is who the big 3 airlines, United, Delta and American, are battling it out to win."
—By CNBC's Phil LeBeau; Follow her on Twitter: @Lebeaucarnews