Boeing Co. may push back the 787 Dreamliner’s entry into service for the seventh time, adding as much as a year to the delay for the composite-plastic jet, Morgan Stanley said.

The plane may not be delivered to the first customer until 2012 because last week’s fire during a flight test may prompt necessary design changes to the electrical system, Heidi Wood, a New York-based analyst with Morgan Stanley, wrote in a note today. She rates the shares “equal-weight.”

The 787 test fleet remains grounded for a ninth day today as the investigation continues into the Nov. 9 electrical fire. The Dreamliner, which is already three years behind schedule, is the first composite-plastic airliner and uses an all-electric system to save fuel.

Boeing, based in Chicago, fell 13 cents to $62.65 at 11:53 a.m. in New York Stock Exchange composite trading. The shares had gained 16 percent this year before today.