Piedmont Airlines will hire 360 new employes for its new reservations facility, boosting its annual estimated payroll to $5 million and making Piedmont one of the largest airline employers in the Washington area.

In its announcement yesterday, Piedmont said 230 of the more than 500 workers that eventually will be employed already are working at the new facility in Reston's Commerce Park.

"We're hiring like mad," Donald M. Shanks, Piedmont's assistant vice president for customer relations, said yesterday, in contrast to many other airlines that are laying off workers. If past experience is an indication, he said he expects between 3,000 and 5,000 to apply for the new Reston reservations-center jobs.

With such a crush anticipated, applications from prospective employes will be screened initially for Piedmont by the Virginia Employment Commission and the Northern Virginia Urban League. Both will administer typing tests to make sure applicants can type 30 words per minute, one of the minimum qualifications for employment. Then, the names of qualified applicants will be forwarded to the Winston-Salem-based airline for screening and final evaluation by Piedmont's personnel department.

Ray Welch, Piedmont's director of personnel, said the airline is required by federal law to list available jobs with state employment agencies. The airline started its Urban League program in Winston-Salem, he said, and when the association worked so well, it was expanded to Northern Virginia.

A five-week training period for those selected will begin Feb. 22. The Reston reservations office is scheduled to begin accepting telephone calls from Piedmont customers on March 29.

Since passage of the Airline Deregulation Act in 1978, Piedmont has been a rising star in the airline industry, using its new freedoms to expand aggressively but carefully. While other carriers' traffic and profits have been affected by flight cutbacks resulting from the air traffic controllers' strike and the recession, Piedmont continues to report record traffic levels and profits.

The airline said yesterday that its passenger traffic in November increased 52 percent over the same month a year ago; its traffic for the first 11 months of 1981 is running 37 percent ahead of last year. Piedmont's earnings for the first nine months of 1981 totaled $23.3 million, up 114 percent over the same period of 1980.

The 19,000-square-foot Reston center, to be open 18 hours a day, will be Piedmont's fourth reservations center; the others are in Winston-Salem, Nashville and Orlando.

Virginia cities were among the first served by Piedmont after it was established in 1948. The airline now boasts that it serves more Virginia cities than any other airline and flies more passengers to and from Virginia communities than all other airlines combined.