Greece lags as U.S. boost helps euro zone shares to halt slide

* Euro STOXX 50 up 0.5 pct; Greece's ATG down 7.4 pct

* Main indexes rebound after strong U.S. data

* Airbus sags; questions over fuel-efficient aircraft demand

By Francesco Canepa and Blaise Robinson

LONDON\PARIS, Dec 11 (Reuters) - Euro zone shares snapped a three-day losing streak on Thursday, taking their lead from gains on Wall Street after some stronger-than-expected consumer spending data from the United States.

Greek shares fell for a third day, however, as upcoming presidential elections sparked fears of political instability that could send the country back into crisis.

If Prime Minister Antonis Samaras fails to secure victory for his presidential candidate, snap national elections would be called which the leftist Syriza party, an opponent of Greece's bailout deal with the European Union and IMF, would likely win.

"The market is pricing in that this political uncertainty will slow down the economic recovery," Natasha Roumantzi, head of analysis at Piraeus Securities in Athens, said.

"If there is no indication that there will be a political solution, then stocks will fall further."

The Athens General Index of Greek stocks was down 7.4 percent at 1601 GMT, taking its fall this week to nearly 20 percent.

Most other euro zone indexes turned higher in late trade in response to the U.S. data which showed consumer spending advancing at a brisk clip in November, with lower gasoline prices giving the holiday shopping season a boost.

The Euro STOX 50 index of euro zone blue chips was up 0.5 percent at 1,358.57 points while the pan-European FTSEurofirst 300 was up 0.1 percent at 1,358.75 points.

The FTSEurofirst 300 had fallen 3.4 percent since the start of the week as worries about Greece and a slump in commodity prices dented investor appetite for assets which depend on global growth.

Among individual movers, Airbus fell 4.3 percent, adding to a 10 percent drop in the previous session after the planemaker predicted flat profits in 2016. That surprised investors who had expected new and recently upgraded models to start boosting results that year.

Zara owner Inditex (Berlin: IXD1.BE - news) bucked the trend, gaining 4.2 percent after posting in-line earnings.

Shares (Frankfurt: DI6.F - news) in CGG (NYSE: CGG - news) tumbled 11.5 percent after a media report said the French government had doubts about a potential tie-up with rival Technip (Paris: FR0000131708 - news) . Technip shares gained 2.9 percent. (Reporting By Francesco Canepa. Editing by Jane Merriman)