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* S&P up 0.16 pct, Dow and Nasdaq flat
* Boeing slides on Ethiopia crash data scrutiny
* Facebook drops as brokerage Needham moves to sidelines
* Apple rises after launching new iPad
* Six of 11 major S&P sectors higher (Updates to early afternoon)
By Medha Singh and Shreyashi Sanyal
March 18 (Reuters) - U.S. stocks flitted between gains and losses on Monday, with losses in Boeing and Facebook limiting gains while investors waited for the Federal Reserve's policy meeting later this week for further clues on the pace of interest rate hikes.
The Fed's two-day policy meeting begins on Tuesday, where the central bank is widely expected to keep interest rates steady and reiterate its "patient" approach to monetary policy.
Investors will be looking for whether the Fed's dot plot, which shows individual committee members' rate views for the coming three years, aligns with the patient approach. Also in focus are details on whether the central bank will continue to shed bond holdings from its balance sheet.
"A lot of it right now is just investors sitting on their hands waiting to see what the Fed has to say which is definitely the highlight of the week," Ryan Nauman, market strategist at Informa Financial Intelligence in Zephyr Cove, Nevada.
Keeping the S&P 500 and Dow's gains in check was Boeing Co, which fell 2.1 percent after Ethiopia said an initial analysis of black boxes showed "clear similarities" in the March 10 plane crash with October's Lion Air accident in Indonesia.
Concerns over the safety of Boeing's marquee MAX fleet led to groundings worldwide last week and shaved off more than 10 percent from the market value of the world's largest planemaker.
Facebook Inc dropped 3.3 percent after a top-rated analyst cut rating on the social media company's stock, dragging the communication services index 0.9 percent lower, the most among the 11 major S&P sectors.
"There is pressure from Facebook, Boeing and news on Brexit but there is no direct news that investors are trading on," Nauman said.
Prime Minister Theresa May's Brexit plans were thrown into turmoil on Monday when the speaker of parliament said she could not put her divorce deal to a new vote unless it was re-presented in a substantially different form.
At 12:51 p.m. ET the Dow Jones Industrial Average was down 6.14 points, or 0.02 percent, at 25,842.73. The S&P 500 was up 4.59 points, or 0.16 percent, at 2,827.07 and the Nasdaq Composite was up 1.54 points, or 0.02 percent, at 7,690.06.
Exxon Mobil Corp rose 1 percent and lifted the energy sector and along with financial stocks provided support to the S&P 500.
A slew of downbeat economic data last week validated the Fed's decision to remain less aggressive on raising rates.
The dovish stance along with hopes that the United States and China will reach an agreement to end their bitter trade dispute boosted the S&P 500 and Nasdaq to five-month highs on Friday and helped notch their best weekly gain this year.
The benchmark index now remains just 3.7 percent away from its all-time closing high in September.
Apple Inc rose 0.7 percent after launching a new 10.5-inch iPad Air in a surprise move on Monday.
Edwards Lifesciences Corp jumped 6.4 percent after trial results showed that the company's non-invasive heart valve replacement system was superior to surgery.
Advancing issues outnumbered decliners for a 1.72-to-1 ratio on the NYSE and a 1.21-to-1 ratio on the Nasdaq.
The S&P index recorded 26 new 52-week highs and one new low, while the Nasdaq recorded 70 new highs and 22 new lows. (Reporting by Medha Singh and Shreyashi Sanyal in Bengaluru; Editing by Shounak Dasgupta)