U.S. stocks were mostly flat on Thursday, as a strong read on third-quarter economic growth raised new questions about monetary policy, though strong results at Visa single-handedly put the Dow in positive territory.

Gross domestic product grew at a 3.5 percent annual rate in the third quarter, beating expectations, though down from the 4.6 percent rate in the second quarter.

The data came a day after the Federal Reserve ended its stimulative bond-buying program. Without quantitative easing - which fueled market gains over recent years, though its end was widely expected - investors are looking to when the central bank will begin raising interest rates. The Fed has said its first rate hike would be dependent on the strength of economic data.

"A strong report, on the heels of a more hawkish tone from the Fed yesterday, has some investors thinking we could see a rake hike faster than might otherwise have been hoped," said Bruce McCain, chief investment strategist at Key Private Bank in Cleveland. "That's dampening the spirits of investors who were hoping for easier monetary conditions for an extended period."

In comments released after a two-day meeting, the U.S. central bank expressed confidence in U.S. economic prospects and dropped a characterization of U.S. labor market slack as "significant."

In a separate report on the economy, jobless claims unexpectedly rose in the latest week, but they remained at levels consistent with a firming labor market.

Visa Inc jumped 8.9 percent to $233.75 as the biggest boost to both the Dow and S&P 500 a day after it reported adjusted earnings that topped expectations, and said the mobile payment industry would be "a great driver" for business.

MasterCard Inc also posted a better-than-expected profit, while revenue was up almost 13 percent.MasterCard added 7.5 percent to $81.69.

So far this reporting season, 75.3 percent of S&P 500 companies have exceeded profit expectations, according to Thomson Reuters data, above the long-term average of 63 percent.

At 9:50 a.m. (1350 GMT) the Dow Jones industrial average rose 103.84 points, or 0.61 percent, to 17,078.15. Without Visa adding 122.8 points to the Dow, the blue-chip index would be in negative territory. The S&P 500 gained 0.47 points, or 0.02 percent, to 1,982.77 and the Nasdaq Composite dropped 3.77 points, or 0.08 percent, to 4,545.46.

Energy shares were the weakest of the day, dropping 0.9 percent alongside a 1.3 percent drop in the price of crude oil. ConocoPhillips fell 0.9 percent to $70.14 despite reporting adjusted earnings that beat expectations.

Declining issues outnumbered advancing ones on the NYSE by 1,439 to 1,262, for a 1.14-to-1 ratio on the downside; on the Nasdaq, 1,170 issues rose and 1,058 fell for a 1.11-to-1 ratio favoring advancers.

The benchmark S&P 500 index was posting 15 new 52-week highs and 4 new lows; the Nasdaq Composite was recording 41 new highs and 14 new lows.