U.S. stocks fell as the prospect of bankruptcy at United Airlines drove down shares of aerospace companies including Boeing, United Technologies and Honeywell International.
"It doesn't bode well if you are in the business of making planes or parts for planes," said John Waterman, chief investment officer at Rittenhouse Financial Services.
The Dow Jones industrial average and the Standard & Poor's 500-stock index both declined for a fifth day, their longest string of losses since Aug. 27-Sept. 3.
The Dow fell 114.57, or 1.3 percent, to 8623.28, and the S&P fell 11.02, or 1.2 percent, to 906.55.
The Nasdaq Stock Market composite index fell 19.60, or 1.4 percent, to 1410.75.
This week's losses threaten to snap the Dow's streak of consecutive weekly gains at eight. The average has dropped 3.1 percent in the past four sessions.
UAL, the parent of United Airlines, plunged $2.12, or 68 percent, to $1. The carrier lost a bid for a $1.8 billion U.S. loan guarantee, pushing it closer to bankruptcy.
UAL shares may be "worthless" by the end of the year, said Jamie Barker of J.P. Morgan Securities.
Boeing, the biggest planemaker, shed 97 cents, to $32.96. United Technologies, a maker of jet engines, lost $1.59, to $61.16. Honeywell, a maker of cockpit controls, lost 67 cents, to $24.33. 3M, which supplies adhesives and electric equipment to airlines, slid $2.10, to $125.90.
General Electric, which makes jet engines and leases aircraft, contributed the most to the S&P 500's loss, dropping 72 cents, to $25.80.
Shares of UAL's rivals, which lobbied against the federal loan guarantee, rose. AMR, parent of American Airlines, rose 54 cents, to $7.58. Continental Airlines added 34 cents, to $8.58. Northwest Airlines climbed 37 cents, to $8.01.
Brokerages including Morgan Stanley and Goldman Sachs Group dropped after Merrill Lynch cut its recommendation on the group to "market weight" from "overweight."
Morgan Stanley declined $1.62, to $42.40, and Goldman Sachs fell $1.90, to $74.45.
Wal-Mart shed $1.42, to $53.02. The world's largest merchant said same-store sales rose 2.6 percent. The company had targeted sales growth between 2 and 4 percent. It expects December sales to rise 3 to 5 percent.
* The New York Stock Exchange composite index fell 4.79, to 482.78; the American Stock Exchange index fell 0.93, to 821.46; and the Russell 2000 index of smaller-company stocks fell 3.08, to 394.45.
* Declining issues outnumbered advancing ones by about 3 to 2 on the NYSE and the Nasdaq. NYSE trading volume fell to 1.26 billion shares, from 1.59 billion on Wednesday, and Nasdaq volume totaled 1.42 billion, down from 1.84 billion.
* The price of the Treasury's 10-year note rose $1.88 per $1,000 invested, and its yield fell to 4.13 percent, from 4.16 percent on Wednesday.
* The dollar rose against the Japanese yen and fell against the euro. In late New York trading, a dollar bought 124.94 yen, up from 124.65 late Wednesday, and a euro bought $1.0009, up from 99.57.
* Light, sweet crude oil for January delivery settled at $27.29 a barrel, up 58 cents, on the New York Mercantile Exchange.
* Gold for current delivery rose to $324.80 a troy ounce, from $322.20 on Wednesday, on the New York Mercantile Exchange's Commodity Exchange.