* Oil falls to 2010 low, Exxon Mobil tumbles
* Airline shares rally on drop in crude prices
* Retailers higher, Wal-Mart boosts Dow
* Indexes notch sixth straight weekly advance
* Dow flat, S&P down 0.3 pct, Nasdaq up 0.1 pct (Updates to close)
By Ryan Vlastelica
NEW YORK, Nov 28 (Reuters) - U.S. stocks ended mostly flat in a holiday-shortened session on Friday as a massive decline in the energy sector offset strength in consumer names, but major indexes rose for a sixth straight week.
Crude oil fell below $68 per barrel a day after OPEC decided not to cut output, which could leave markets oversupplied. The 7 percent decline was the biggest one-day drop since May 2011, with prices lowest since 2010.
"Crude seems to have no floor right now, and we could easily see the price drop into the low $60s," said Tony Roth, chief investment officer at Wilmington Trust in Wilmington, Delaware.
The Energy Select Sector SPDR exchange-traded fund fell 6.4 percent to $79.82 while the S&P energy index lost 6.3 percent, extending its run as the worst-performing S&P industry group of the year. Exxon Mobil Corp lost 4.2 percent to $90.54 while Chevron Corp fell 5.4 percent to $108.87; both are Dow components.
Shale energy companies saw outsized declines, as $70 oil is considered the level at which shale becomes an unprofitable alternative. Denbury Resources, QEP Resources and Newfield Exploration all lost more than 15 percent.
Oil weakness boosted airlines, which are inversely correlated to oil prices. Southwest Airlines rose 6.5 percent to $41.82 as the S&P 500's biggest percentage gainer, followed by Delta Air Lines, up 5.5 percent to $46.67.
Retailers rallied as lower gas prices could increase consumer spending. Wal-Mart Stores Inc rose 3 percent to $87.54, boosting the Dow, while the S&P 500 Retailing index was up 1.4 percent.
" this low should be very additive to economic activity, not just with gas prices but across the economy," said Roth, who oversees $80 billion in assets. "Early holiday shopping numbers should come in pretty strong."
The Dow Jones industrial average rose 0.49 points to 17,828.24, the S&P 500 lost 5.27 points, or 0.25 percent, to 2,067.56 and the Nasdaq Composite added 4.31 points, or 0.09 percent, to 4,791.63.
Major indexes rose for a sixth straight week, the S&P's longest streak since November 2013. For the week, the Dow rose 0.1 percent, the S&P rose 0.2 percent and the Nasdaq rose 1.7 percent.
For November, the Dow rose 2.5 percent, the S&P added 2.5 percent and the Nasdaq 3.5 percent.
NYSE decliners issues outnumbered advancers 1,846 to 1,137, for a 1.62-to-1 ratio; on the Nasdaq, 1,777 issues fell and 875 advanced, for a 2.03-to-1 ratio.
The S&P 500 posted 152 new 52-week highs and 21 new lows; the Nasdaq Composite recorded 163 new highs and 80 new lows.
About 4.2 billion shares traded on all U.S. platforms, according to BATS exchange data. (Editing by Nick Zieminski)