PITTSBURGH (AP) - Shares of Boeing Co. slid to a three-year low Thursday, amid concerns over high oil prices and a possible strike at the company's commercial airplane business.

Shares of the Chicago-based company declined $2.71, or 4.3 percent, to close at $61.11. Earlier Thursday, the stock fell to $61.01, its lowest point since June 2005.

Boeing stock has dropped sharply from its all-time high of $107.23 in July last year as the price of oil has soared.

Higher fuel costs have hampered airlines and air cargo companies, especially in the U.S., and some carriers have begun delaying delivery of planes as they struggle to control costs.

The stock has "certainly had a rough time" in recent months, mostly because of delays related to the long-awaited 787 jetliner and fears over high oil prices, JSA Research analyst Paul Nisbet said in an interview.

In a note to investors, Banc of America Securities analyst Harry Nourse wrote of a "looming" strike by union machinists working for Boeing's commercial airplane business.

"Following a recent conference call with union officials, we believe that there is a high chance (greater than 70 percent) of a work stoppage at (Boeing Commercial Airplanes) in the near future," he wrote.

A Boeing spokesman, Tim Healy, said the company had adopted a new approach that entailed meeting early with union representatives and discussing critical issues, such as wages and benefits.

"We think it's going well ... and we're driving toward an agreement," he said.

In 2005, about 18,400 machinists struck for four weeks, forcing the company to halt production of commercial airplanes. The machinists assemble Boeing's commercial planes and some key components.

Union officials have said the most important issues this time include job security, general wage increases, a guaranteed pension plan and improving health care benefits.

The machinists are expected to vote on a new labor contract Sept. 3.