With Boeing ( BA) raising first-quarter guidance recently, the company has provided more questions than answers, making the aerospace giant's April 28 earnings release a can't miss for shareholders.

Boeing's preannouncement Thursday gives Wall Street a general idea of what the company's numbers will look like -- but Boeing didn't provide specifics as to how or why the company will top current first-quarter estimates of 44 cents a share. With brokerages awaiting the rationale for the upside surprise, new CEO Harry Stonecipher, who is at the helm of the company for his first full quarter, will take center stage, trying to repair Boeing's reputation on Wall Street.

There are two schools of thought on Boeing's outperformance. Citigroup Smith Barney's George Shapiro said Boeing's better-than-expected earnings are due to "Stonecipher's emphasis on execution." In his view, earnings may be driven by rising margins in Boeing's commercial aircraft unit or strong growth in military revenues -- especially given the strength in General Dynamics' ( GD) military revenue.

But with the March durable goods data released Friday showing that nondefense aircraft orders rose 11.7%, while defense aircraft demand fell 27.7% in March, Boeing's upside surprise could be much ado about nothing, with the company's business outlook essentially unchanged. This week, Boeing executives told investors that commercial aircraft deliveries will likely be around 285, flat with last year's level.

"The fact that the release did not address full-year estimates leads us to believe that the first-quarter surprise may partly be due to timing issues," said Byron Callan, analyst at Merrill Lynch, adding that Boeing's earnings could be as high as 60 cents a share. "In our recollection, this is the first time Boeing has issued such a release, even though there have been prior quarters when it has exceeded analysts' estimates."

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