Quality Inns International Inc. reported yesterday decreased earnings for the third quarter but much higher profits for the most recent nine-month period.

Net income for the third quarter ended May 31 was $1.7 million (67 cents a share) compared with $2 million (73 cents) last year. Revenues rose to $17.9 million, up from $17.4 million.

One reason for the earnings-per-share decrease during the third quarter was the higher tax rate of 44 percent in 1980, compared with 29 percent the previous year, the company said in a statement.

Nine-month results were better, with net income of $3.9 million ($1.49) compared with $2.7 million ($1.01) a year earlier. Revenues rose from $45 million to $48 million.

The company should finish the year in a "favorable position" said Stewart Bainum, chairman of Quality, the world's seventh-largest lodging chain. The company's perennially strong fourth quarter is yet to come, Bainum noted.

"I am optimistic that the present recessionary state of the economy will not significantly erode our performance level," he continued. "We expect our moderately priced inns to become even more attractive to travelers during these highly inflationary times."

USAir Inc, reported net income of $6.8 million (54 cents a share) for May, up from $5.3 million (42 cents) a year ago. Revenues were $80.2 million compared with $62 million.

Earnings for the five months ended May 31 were $18.8 million ($1.45) compared with $4.8 million (32 cents). Revenues for the period were $371 million, up from $263 million.