????by Michael V. Copeland

????Boeing’s long-delayed 787 Dreamliner finally took flight on Tuesday to the ecstatic cheers of thousands watching from a wet runway at Paine Field in Everett, WA. The composite wings flexed, and the Rolls-Royce engines roared as the first entirely new commercial jet from the Boeing Co. since launching the 777 in 1995 headed out toward the Pacific for a four-hour spin.

????There are thousands of hours more to go in flight tests and other system tests, before Boeing (BA/$55) can deliver the first of the fuel-efficient jets to All Nippon Airways. Boeing plans on putting the first of 840 jets ordered, worth some $140 billion, in customer hands by the end of 2010. The plane’s first flight is clearly a huge step toward getting there. But with a program already more than two years behind schedule, customers, and Wall Street, will be keeping on a close watch on the next phase of testing to see if the planes are likely to be delivered on time.

????Even as the plane was still on its maiden flight, Morgan Stanley analyst Heidi Wood cautioned her clients to, “sell the news.” Wood, who has an “underweight” rating on Boeing and a $43 price target on shares, cautions that if investors behave like they did the last time a new Boeing jumbo jet performed its first flight when the 777 debuted, Boeing shares could see a hit. In the 30 trading days leading up to the Dreamliner’s first flight, Boeing stock rallied 9% relative to the S&P 500 (it’s up 30% so far in 2009).

????Back in 1995, Boeing shares rallied 6% (relative to the S&P 500) ahead of the 777's first flight. That was followed by 11% percent underperformance (again compared to the S&P 500) for the 60 trading days after. “If history,repeats itself, Boeing may see a shift in sentiment towards the downside post 787 first flight,” Wood told clients. On Tuesday, Boeing shares closed down almost 1%.

????So if you own Boeing shares, keep a close eye. What you want to see is the next nine months going flawlessly. More than anything, Boeing needs to get its fancy new planes into the hands of customers. Any more delays, and Boeing shares take a hit. If you are a passenger, you’ll want to keep tabs on things too.

????When these jets start serving commercial routes, it’s going to be an upgrade like you haven’t experienced since they put those screens into the back of headsets.