Chicago ? Boeing Co. said Wednesday that continuing repercussions from the aviation industry slump have forced it to further lower its forecasts for profit and revenue, and could result in more layoffs.

The warning came as Boeing released third-quarter results confirming a steep drop in business at its commercial airplanes division, the key factor in a 43 percent decline in net profit from the year-ago quarter.

“We are in a dramatically changed business environment which began more than a year ago” with the Sept. 11 attacks, chairman and CEO Phil Condit said. “Our commercial markets remain impacted by the economy, by the financial markets and by the prospect of military action in Iraq,” in addition to the slow recovery of travel and airline profitability problems, he said.

The company reduced its estimate of 2003 revenues to $50 billion from $52 billion and said profit margins will be lower than previously expected for both 2002 and 2003.

It also lowered its airplane delivery outlook for 2003, saying it expects between 275 and 285 planes instead of the previous 275 to 300, and said 2004 deliveries will be in a similar range.

The pessimistic forecasts sent Boeing shares down $1.65, or 5 percent, to close at $30.50.

“They were looking through their rose-colored glasses and hoping all the marginal things would go their way,” said analyst Paul Nisbet of JSA Research. “They aren’t.”

Net earnings for the July-through-September period were $372 million, or 46 cents a share, down from $650 million, or 80 cents a share, a year earlier.

Excluding nonrecurring items which included a $63 million writedown of its investment in Teledesic and after-tax gains of $67 million per-share earnings, also of 46 cents, met the recently reduced consensus estimate of analysts surveyed by Thomson First Call.

Revenues fell 7 percent to $12.7 billion from $13.7 billion.

In a symbol of the aerospace giant’s increasing diversification, revenue from its Seattle plane-manufacturing business, at $6.1 billion, accounted for less than half of overall revenues a trend the company said was expected to apply for all of 2003.

With no end in sight to the downturn, Condit acknowledged that more layoffs are possible beyond the 30,000 expected to be completed by year’s end within the Seattle unit.

Boeing has a plant in Wichita and is Kansas’ largest private employer.