* FTSEurofirst 300 off 1.5 pct, cyclical stocks weigh
* Some 50 bln euros wiped off euro zone benchmarks
* Airlines down on bird flu concerns
By Tricia Wright
LONDON, Dec 3 (Reuters) - European stocks dropped on Tuesday, suffering their biggest falls since August after recent robust U.S. data raised concern that the Federal Reserve will cut its equity-friendly stimulus sooner rather than later.
The FTSEurofirst 300 ended down 1.5 percent at 1,280.85 points, its lowest closing level since Oct. 23, and its most severe one-day percentage drop since Aug. 27. This left it 2.8 percent shy of a 5-1/2 year high of 1,316.42 hit in early November.
The broad-based sell-off wiped out more than 50 billion euros ($67.78 billion) in market capitalisation for euro zone benchmark indexes - Germany's DAX, France's CAC-40 , Spain's IBEX and Italy's FTSE MIB combined.
Cyclical sectors were the biggest losers. Traders blamed stronger than expected U.S. manufacturing and construction spending data on Monday for the broad market weakness.
A robust economy is normally good for equities, but the recent improving outlook could lead to an early reduction in the Fed's bond-buying programme, which has supported the rally in stocks.
Investors are aware the central bank will start reducing stimulus at some point, but question marks remain about the timetable for doing so. Most expect the announcement in March.
The Fed has said it will begin to scale back its programme when certain economic data releases meet its targets, with Friday's November jobs report expected to provide some clues.
"I think tapering is not going to happen in December; first of all I'm not so sure (Friday's) figure will be so strong," said Philippe Gijsels, head of research at BNP Paribas Fortis Global Markets.
"I would even be willing for people who want to play the short term ... to buy into the figure because I think maybe we will have a rally afterwards."
Airlines came under pressure after the first human case of H7N9 bird flu in Hong Kong fanned concern that the virus is continuing to spread beyond mainland China's borders.
Air France-KLM fell 4.2 percent and Germany's Lufthansa was down 3.8 percent.
There was profit-taking in autos, off 2.3 percent. They have risen by a third in 2013, making them the best performers.
Still, analysts see scope for more gains. JPMorgan is bullish on the sector for 2014 as it expects a recovery in the European, Chinese and North American car markets will support higher earnings.