Updated from 11:15 a.m. EDTShares of Pemco Aviation ( PAGI) were among the Nasdaq's losers Monday after the company posted disappointing second-quarter earnings results. The aircraft-maintenance company posted a second-quarter loss of 28 cents a share on sales of $43.5 million. A year ago, it earned 49 cents a share on sales of $47.3 million. The company's earnings before interest, taxes, depreciation and amortization, or EBITDA, came in much lower than expected. Instead of $5 million to $6 million in EBITDA, as the company had expected, it reported a loss of $300,000. The U.S. Air Force's new requirements associated with the maintenance of its KC-135 tanker fleet resulted in higher-than-expected costs and production delays for the company. Shares of Pemco Aviation traded down $3.77, or 12.6%, to $26.13. 21st Century ( TCHC) fell after the insurance company projected its losses from Hurricane Charley and revised earnings guidance. The company's total exposure is estimated to be between 1,000 and 1,500 claims, which would result in a $5 million to $6 million charge, or about $1.25 a share during the third quarter. As a result of the charge, 21st Century now expects to post a profit of $2.50 a share for 2004. Excluding the charge, analysts had expected it to post a profit of $3.75 a share. Looking ahead, the company reaffirmed earnings estimates of $4.50 to $5 a share for 2005. Shares of 21st Century traded down $1.45, or 7.3%, to $18.30. Shares of Arch Coal ( ACI) rose after a federal judge rejected the Federal Trade Commission's request for a preliminary injunction that would have blocked Arch's acquisition of Triton Coal. Arch said the FTC has the right to seek an emergency stay of the decision. Arch agreed to not complete the transaction for two days. Shares of Arch Coal traded up $2.33, or 7.7%, to $32.73.