USAIR <U> HAS NO COMMENT ON TWA <TWA> OFFER USAir Group Inc said it had no comment on an offer it received from Trans World Airlines to buy USAir for 52 dlrs cash per share. USAir spokesman David Shipley also declined comment on Piedmont Aviation Inc <PIE>. USAir has offered 71 dlrs cash per share for half of Piedmont's stock, and 73 dlrs in its own stock for the balance. Piedmont also received an offer from Norfolk Southern Corp <NSC> of 65 dlrs cash per share. Piedmont's board was meeting today, but the company declined to say what was on the agenda. A spokesman said he could not comment on the twa action. A Norfolk Southern Corp <NSC> spokesman said the company had no comment on TWA's offer for USAir or on its proposal to negotiate a three-way merger between TWA, USAir and Piedmont. "We don't have all the details," a Norfolk Southern spokesman said. The company's 65 dlr-a-share cash offer for Piedmont stands, he said. In its offer, TWA said as an alternative to a merger with USAir, it would be interested in discussing a three-way combination among USAir, Piedmont and TWA. It said the three-way merger would serve the best interests of the shareholders of all three companies, employees and consumers.