USAir Group reported a $75 million net loss for the three months ended in June, the fourth consecutive quarterly loss for the Arlington-based carrier.

Airline industry analysts said that the results were not surprising given the sluggishness in sales throughout the industry and higher operating costs. Earlier this month, AMR Corp., the parent company of American Airlines, reported a 27.4 percent drop in second-quarter earnings.

The airline industry has been suffering from a downturn since about mid-1989 as a result of a slowdown in domestic traffic and increased expenditures. USAir Chairman Edwin I. Colodny predicted in January that the airline might report a loss for 1990. Last year, it reported a net loss of $63 million.

USAir revenue for the second quarter was $1.7 billion, down slightly from the same period a year ago, while expenses were up nearly $120 million. That net loss worked out to $1.86 per share, compared with earnings of $2.29 in 1989.

For the first six months of this year, USAir has piled up a loss of $113 million. While revenue for that period increased about $30 million over the same period a year ago, expenses soared by $390 million, driven by increases in fuel (up 17 percent) and personnel (up 20 percent) costs.

Figured on an operating basis -- without such things as interest payments, depreciation and tax calculations -- USAir continued to show a profit during the second quarter. Quarterly operating income was $59 million, compared with operating income of $201 million in 1989.

Some of the difference between the operating profit and the net loss reflected a $90 million adjustment in a tax credit that the airline took in the first quarter. The company, which had taken a $134 million tax credit, changed the basis on which it was computing the credit from anticipated results to actual results. As a result, in the second quarter, the tax credit was adjusted downward.

Although USAir may still be having difficulties winning back customers who experienced poor on-time performance following its merger last year with Piedmont Aviation, the airline has improved operationally, said First Boston analyst Paul Karos.