(Repeats to add USA to slug, with no change to headline ot text)
* Palm gives weak outlook, to sell shares
* Quadruple witching on tap
* Futures: S&P down 0.6 pts, Dow up 5, Nasdaq up 2.25
NEW YORK, Sept 18 (Reuters) - U.S. stock index futures were flat on Friday as investors sought to determine whether a pullback is on the horizon after a 6-month rally and braced for options expiration.
* Analysts said investors were trying to decide if further market gains were justified, with the benchmark S&P 500 now up 58 percent since early March lows.
* S&P 500 futures fell 0.6 points and were slightly above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures rose 5 points, and Nasdaq 100 futures gained 2.25 points.
* Robust sales of the new Pre smartphone helped Palm Inc post a smaller-than-expected loss, but a tepid second-quarter sales forecast and a plan to sell more shares sent its stock down nearly 2 percent after the close on Thursday.
* Friday marks the quarterly expiration and settlement of four different types of September equity futures and options contracts -- a convergence known as quadruple witching that can lead to greater volume and volatility as traders unwind positions.
* AMR Corp's American Airlines will team up with British Airways Plc and Qantas Airways Ltd to expand an alliance with cash-strapped Japan Airlines Corp, two people with direct knowledge of the talks said.
* The proposal, which would include a capital injection from American Air but may not bring money from British Airways or Qantas, is aimed at thwarting Delta Air Lines Inc, a member of a rival alliance that is also in talks to invest in JAL.
* Boeing Co will garner attention after the head of Airbus said in remarks in the Wall Street Journal Friday that the European planemaker faces two further "difficult" years and does not rule out making more production cuts to adjust to demand.
* Penn National Gaming Inc is in negotiations to buy the bankrupt Fontainebleau Las Vegas casino and resort, the Journal reported, citing a source with knowledge of the negotiations.
* European shares were mixed on Friday after hitting an 11-month peak in the previous session, with banks slipping after British regulators set tougher-than-expected terms on Lloyds Banking Group PLC's exit from a government scheme.
* Asian stocks retreated from 13-month highs on Friday and commodity prices dipped after U.S. data gave a conflicting picture about the strength of a recovery.
* U.S. stocks slipped Thursday after a three-day run-up on concern that recent gains were overextended.
* The Dow Jones industrial average fell 7.79 points, or 0.08 percent, to end at 9,783.92. The Standard & Poor's 500 Index was down 3.27 points, or 0.31 percent, at 1,065.49. The Nasdaq Composite Index was down 6.40 points, or 0.30 percent, at 2,126.75.