Continental, United merge

NEW YORK — Stocks started off October on a positive note following mostly good news on the economy.

   United Airlines and Continental closed a deal to create the world’s biggest airline Friday. Shares of the newly combined company, United Continental Holdings Inc., jumped $1.04, or 4.4 percent, to $24.70.

  Shares of big manufacturing companies like Boeing Co., General Electric Co. and 3M Co. rose Friday after the Institute for Supply Management said its manufacturing index showed that factory activity was still expanding in September, although not quite as fast as analysts had hoped and slightly slower than the month before.

 Stock indexes started the day higher but gave up some of their gains late in the day. The market is coming off a major surge that brought the Dow Jones industrial average up 10.4 percent in the third quarter, and its upward momentum may be waning.