April 20 (Reuters) - Union Pacific Corp's (UNP.N) chief executive officer said on Thursday the railroad operator was considering slowing down the pace of hiring in the second half of the year amid a cloudy economic outlook, becoming the latest U.S. company to evaluate its staffing plans. CEO Lance Fritz told Reuters in an interview the outlook was turning a "little cloudier" for consumer-facing companies, which is making railroad volume difficult to predict. A possible slowdown in hiring comes at a time when railroads are struggling to move cargo on time, which has invited severe criticisms from regulators and customers. Shares of Union Pacific, which connects West Coast ports to key terminals such as Chicago, lost its gains in the day to trade flat in the afternoon session. Operating revenue for the quarter ended March 31 rose 3% to $6.06 billion, in line with analysts' estimates.

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