Let's close this duel by singing the JetBlue (NASDAQ:JBLU) blues.

In 2004, 75% of JetBlue's flights had JFK or LaGuardia as their destination or origin. That's a potentially lethal concentration of business.

At the end of 2004, JetBlue had committed to spend $7.3 billion on 214 additional aircraft over the next seven years. That's a gigantic commitment for debt or equity financing for a company with trailing annual revenue of only $1.5 billion.

The company's fleet of aircraft had an average age of 2.2 years at the end of 2004. Maintenance costs are low today. What happens to profitability when major overall costs start to hit?

In 2004, 23% of total available seat miles were generated by US airlines in bankruptcy. That figure will be even higher this year. As these companies exit bankruptcy with lower operating costs, there may be new competitive pressures put on JetBlue and its already low 2.1% trailing annual profit margins.

So far, JetBlue has copied Southwest Airlines' (NYSE:LUV) tried-and-true operating strategy of having a single type of aircraft. On Tuesday, JetBlue received the first of 26 Embraer (NYSE:ERJ) aircraft it will put in service by the end of 2006. Is this smaller 100-seat jet necessary, and will it be a hit with passengers?

New competition wants in. Virgin America will fly Airbus A320 aircraft that will focus on comfort, entertainment, and value. That sounds very similar to JetBlue. If Virgin gets financing, operations should start in 2006.

If all that doesn't make you blue, JetBlue is selling at a stratospheric 69 times trailing earnings. There isn't enough earnings growth ahead to justify a major move upward in the stock.

You're not done. This is just a quarter of the Duel! Don't miss W.D.'s bearish opening salvo, John Reeves' bullish comeback, or John's final word. When you're done, you're still not done. You can vote and let us know who you think won this Duel.

JetBlue and Embraer have been recommended to Motley Fool Stock Advisor subscribers.

Fool contributor W.D. Crotty does not own shares in any of the companies mentioned. Click here to see the Motley Fool's disclosure policy.