USAIR <U> CLEARED TO BUY PIEDMONT <PIE> SHARES USAir Group Inc said the U.S. Department of Transportation has issued an order allowing it to purchase and hold in a voting trust the 9,309,394 Piedmont Aviation Inc shares USAir is seeking in its current 69 dlr per share tender offer. The company said the new order supersedes an order issued by the department last Friday that would have required USAir to sell within one week of expiration of the tender any Piedmont shares it held in excess of 51 pct of the Piedmont stock then outstanding. The company said the 9,309,394 Piedmont shares, together with the 2,292,599 Piedmont shares already owned by USAir, constitute about 50.1 pct of Piedmont's shares on a fully-diluted basius but about 61.0 pct of shares currently outstanding. The shares are to be held in a voting trust pending the department's review of USAir's application to obtain control of Piedmont.