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Goldman Sachs is bullish on United Airlines (UAL - Get Report) , predicting the stock will rebound in the half of the year.

United shares were rising 0.86% to $82.55 Thursday after Goldman upgraded the stock to buy from neutral and maintaining its $108 price target.

"Given [United]'s share price decline since we initiated in November 2018, it now has one of the highest levels of upside potential to our price target in our coverage universe," said Goldman in a note to clients. "Additionally, we are of the view that United is likely within 12 to 36 months of signing a new contract with improved economics with its co-brand credit card partner Chase."

Goldman analysts also downgraded budget flier Spirit Airlines (SAVE - Get Report)   saying that the company's revenue momentum would not match its previous expectations. The firm downgraded Spirit to neutral from buy. 

Spirit shares were down 1.95% to $49.44.