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* Boeing shares fall after 737 production cut
* S&P 500 pauses after 7-day run of gains
* GE slides after JPM downgrades to "underweight"
* Energy stocks mirror gains in oil prices
* Indexes down: Dow 0.51%, S&P 0.21%, Nasdaq 0.14% (Updates to early afternoon)
By Shreyashi Sanyal and Sruthi Shankar
April 8 (Reuters) - U.S. stocks headed lower on Monday, following the S&P 500's seven-day winning streak, as Boeing's shares took a hit and investors braced for what could be the first decline in corporate earnings since 2016.
Shares of the U.S. planemaker fell 4.7%, pulling the S&P industrials sector down 1%, after the company said it would cut production of its 737 MAX aircraft by nearly 20%.
Southwest Airlines Co fell 2.7% after the carrier said it was pulling out all 737 MAX jets from its flight schedules through June 7, extending its earlier timeline by a week.
The sector was also pressured by General Electric Co's 8.4% tumble after J.P.Morgan downgraded the conglomerate's shares to "underweight".
The recent run of gains in U.S. stocks has taken the S&P 500 within 2% of its record closing high hit in September, supported by the Federal Reserve's decision to hold off on interest rate hikes in 2019 and on hopes of a trade deal with China.
However, lowered earnings expectations and worries about an economic slowdown are starting to dampen investor enthusiasm.
"We've seen some progress on trade, the Fed has backed off on interest rate increases, we saw job growth come back. But none of that matters if companies aren't making money and that's been one of the major concerns in the market," said Brad McMillan, chief investment officer for Commonwealth Financial Network.
Major banks are slated to kick off first-quarter earnings season later in the week and analysts expect a 2.3 percent fall in profits at S&P 500 companies in the first quarter, according to Refinitiv data.
At 12:43 p.m. ET the Dow Jones Industrial Average was down 135.20 points, or 0.51%, at 26,289.79, the S&P 500 was down 6.00 points, or 0.21%, at 2,886.74 and the Nasdaq Composite was down 11.37 points, or 0.14%, at 7,927.33.
Seven of the 11 major S&P sectors were lower. Energy stocks , among a few bright spots, posted a 0.40% rise as oil prices hit a five-month high.
Symantec Corp jumped 6% after a report that Goldman Sachs raised its rating on the cyber security firm's stock to "buy" from "neutral".
Procter & Gamble Co climbed 1.2% after Wells Fargo raised its rating on the company's shares to "outperform" from "market perform".
Declining issues outnumbered advancers for a 1.18-to-1 ratio on the NYSE and for a 1.41-to-1 ratio on the Nasdaq.
The S&P index recorded 23 new 52-week highs and no new lows, while the Nasdaq recorded 45 new highs and 22 new lows. (Reporting by Shreyashi Sanyal and Sruthi Shankar in Bengaluru; Editing by Anil D'Silva)