Northwest Airlines said it plans to buy as many as 325 CFM56-5 engines worth $1.25 billion to power the A320 and A340 aircraft it has on order from Airbus Industrie. The CFM56-5 is manufactured jointly by General Electric and SNECMA, a French aircraft company . . . Steel imports in the first quarter fell 10.4% from the 5.7 million tons shipped a year ago, the American Institute of Imported Steel reported . . . Coast RV Inc. began trading on the Amex under the symbol CRV . . . Oakland-based World Airways has acquired Key Airlines from Presidential Airways of Washington for $18 million. Key provides contract flight operations for several military and civilian customers.