A federal appeals court has upheld a ruling undercutting a prospective class action against Microsoft for allegedly underpaying and not promoting nearly 8,600 female employees.

A panel for the U.S. Court of Appeals for the Ninth Circuit sided with a team from Orrick, Herrington & Sutcliffe in affirming a 2018 decision not to certify the class accusing Microsoft of systematically discriminating against women in both pay and promotions. U.S. District Judge James Robart of the Western District of Washington found there were no uniform policies or job descriptions that tied the proposed class together.

"The allegedly discriminatory pay and promotion decisions in the instant case do not present common questions because the proposed class consists of more than 8,600 women, who held more than 8,000 different positions in facilities throughout the United States," the panel wrote in the unpublished ruling Tuesday. "Further, appellants failed to identify a common mode of discretion throughout Microsoft because the individual managers had broad discretion over how to conduct the Calibration Meetings/People Discussions, as well as over the decisions that they made at those meetings."

More than 30 civil rights and labor groups filed an amicus brief urging the panel to reverse Robart's ruling. The U.S. Chamber of Commerce and the Washington Legal Foundation were among the groups that filed amicus briefs siding with Microsoft.

The panel was composed of Ninth Circuit Judges Richard Paez and Johnnie Rawlinson, and U.S. District Judge Leslie Kobayashi of Hawaii sitting by designation.

Attorneys from Lieff Cabraser Heimann & Bernstein represented the plaintiffs, and appeared to face an uphill fight during oral arguments in November.

The panelists peppered Lieff Cabraser partner Anne Shaver with questions during the hearing about how Microsoft evaluated its employees, and pushed her to identify the policy at issue.

"I don't feel there is a policy that's been pointed out," Rawlinson said at one point during the hearing.

Orrick partner Lynne Hermle handled arguments for Microsoft.

The case is one of several gender bias lawsuits that have targeted the technology industry. Other companies that have faced scrutiny include Google, Oracle, Twitter and Uber Technologies.

A California appellate court earlier in December refused to overturn a ruling denying class certification in a case against Twitter brought on behalf of 135 female software engineers who claimed they were disproportionately passed over for promotions. Orrick represents Twitter in that case.