Arconic Inc. shares slid 9% in premarket trade Monday, after the maker of aluminum for the car, aeroplane and other industries offered earnings guidance that fell short of consensus estimates. Arconic said it had net income of $143 million, or 29 cents a share, in the first quarter, down from $322 million, or 65 cents a share, in the year-earlier period. Adjusted per-share earnings came to 34 cents a share, a penny ahead of the FactSet consensus. Revenue rose 8% to $3.4 billion, also ahead of the FactSet consensus of $3.3 billion. The company said earnings were hit by the unfavorable impact of higher aluminum prices, shortfalls in the company’s rings, disks and global rolled products business, unfavorable aerospace wide-body production mix, and the inventory impact of the new pension accounting standard, all of which more than offset volume gains and net cost savings. Chief Executive Chip Blankenship said he had visited several of the company’s sites in the quarter and found them lacking. “It is clear that we have areas in need of operational improvement. To ensure all businesses execute consistently, we are deploying targeted capital and expertise to close gaps. In addition, we are updating our full year 2018 guidance due to rising aluminum prices and my deeper understanding of our operations,” he said. 2018 will be a year of transition, he added. The company is now expecting full-year adjusted EPS of $1.17 to $1.27, below the FactSet consensus of $1.49. Revenue is expected to range from $13.7 billion to $14.0 billion, compared with a consensus of $13.5 billion. Shares are down 18% in the last 12 months, while the S&P 500 has gained 12%.