NEW YORK - Shares of U.S. airlines rebounded on Friday following three straight days of losses after an analyst upgraded five carriers' stocks to a buy.

The Arca Airline Index .XAL rose about 3 percent, led by shares of United Airlines parent UAL Corp and U.S. Airways.

UAL jumped about 7 percent, or 63 cents, to $9.46, while U.S. Airways rose 3.7 percent, or 18 cents, to $5.09 in early trading on the New York Stock Exchange.

Many U.S. carriers have bolstered their balance sheets in recent months, helping them avert bankruptcy risk in the near-term, UBS analyst Kevin Crissey wrote in a note to clients, which was released to clients Thursday after the market closed.

Crissey also upgraded Continental Airlines, American Airlines parent AMR Corp and Alaska Air Group, all of which jumped more than 4 percent.

(Reporting by Deepa Seetharaman; Editing by Phil Berlowitz)