* General Dynamics off after jet crashes in test flight
* Southwest Airlines shares fall after plane groundings
* Pfizer to sell unit to KKR for about $2.4 billion
* Futures up: Dow 20 pts, S&P 3 pts, Nasdaq 9.5 pts (Updates prices, comment)
By Rodrigo Campos
NEW YORK, April 4 (Reuters) - U.S. stocks were set to open slightly higher on Monday, with the S&P 500 facing a level where selling has clustered in recent sessions.
S&P 500 futures traded in a tight range below 1,333. The benchmark has been unable to close above that level since mid-February, although the index briefly pierced it on Friday.
That level is double the 12-year low hit in March 2009 and is not far from 1,344, the S&P's 2011 high and its highest since June 2008.
On Friday, the S&P closed its best two-week period since December and the Dow industrials hit its highest intraday level since June 2008.
"The speed with which we moved up is putting a bit of a curb on a further rally," said Rick Meckler, president of investment firm LibertyView Capital Management in New York.
"Certainly there are plenty of traders who will be using this run-up to try and take profits and get back at a better point. It's hard to maintain the speed of this advance," he said.
The lack of significant economic data on Monday, nuclear and other quake-related problems in Japan and unrest in Libya, Syria and other states in the oil-rich region could translate into low volumes in Wall Street. Last week was the lowest in volume so far in 2011.
S&P 500 futures rose 3 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures gained 20 points and Nasdaq 100 futures added 9.5 points.
Shares of defense contractor General Dynamics dropped 3.7 percent to $74.55 premarket after its business-jet unit Gulfstream Aerospace said a jet crashed during a test flight on Saturday, killing two pilots and two flight-test engineers.
Southwest Airlines Co shares dropped 2.8 percent to $12.31 in premarket trading after planes were grounded for inspection. A U.S. safety investigator said on Sunday evidence of widespread fuselage cracks was found on a jet that made an emergency landing with a hole in the cabin.
In the latest acquisition news, Pfizer Inc rose 0.7 percent to $20.53 after the drugmaker agreed to sell its Capsugel unit, the world's largest maker of hard capsules, to private equity firm KKR & Co for nearly $2.4 billion.
"Today will be influenced a little by takeovers in the marketplace and further gains in commodities," LibertyView's Meckler said.
Nasdaq OMX Group Inc and IntercontinentalExchange Inc face serious hurdles to their unsolicited bid for NYSE Euronext, that could prevent their offer from being accepted..
Deutsche Boerse is holding off on making any decision as to whether to raise its rival offer for NYSE Euronext, two sources familiar with Deutsche Boerse's thinking said on Monday.. Shares of NYSE Euronext dipped 0.9 percent to $39.25 premarket.
Nervousness over the political unrest in the Middle East and North Africa helped lift oil prices, with Brent crude rising to near $120 a barrel and U.S. crude hitting a 2-1/2-year high above $108. (Reporting by Rodrigo Campos; Editin