<ARTICLE> 5 <MULTIPLIER> 1,000 <PERIOD-TYPE> 6-MOS <FISCAL-YEAR-END> DEC-31-1997 <PERIOD-START> JAN-01-1997 <PERIOD-END> JUN-30-1997 <CASH> 13,857 <SECURITIES> 0 <RECEIVABLES> 315,608 <ALLOWANCES> 8,855 <INVENTORY> 37,734 <CURRENT-ASSETS> 401,771 <PP&E> 1,724,342 <DEPRECIATION> 859,337 <TOTAL-ASSETS> 1,290,998 <CURRENT-LIABILITIES> 294,422 <BONDS> 435,285 <PREFERRED-MANDATORY> 0 <PREFERRED> 0 <COMMON> 21,686 <OTHER-SE> 452,060 <TOTAL-LIABILITY-AND-EQUITY> 1,290,998 <SALES> 0 <TOTAL-REVENUES> 1,368,306 <CGS> 0 <TOTAL-COSTS> 1,281,015 <OTHER-EXPENSES> 0 <LOSS-PROVISION> 0 <INTEREST-EXPENSE> 16,496 <INCOME-PRETAX> 70,795 <INCOME-TAX> 28,134 <INCOME-CONTINUING> 42,661 <DISCONTINUED> 0 <EXTRAORDINARY> 0 <CHANGES> 0 <NET-INCOME> 42,661 <EPS-PRIMARY> 1.97 <EPS-DILUTED> 1.78