Wiley Rein is fighting back against claims that it overbilled a Bethesda-based software developer in a legal battle the developer lost, accusing its former client of stiffing it on the bill.

The Washington, D.C.-based law firm has filed a counterclaim against AirFacts, an airfare auditing software developer, alleging it hasn't paid at least $221,857.08 in legal fees that the developer racked up in a lawsuit against a former employee.

Wiley Rein has until Thursday to file its motion to strike AirFacts' answer to its Dec. 20 counterclaim. The law firm contends that AirFacts' answer violated a local court rule that spells out how pleadings are structured. However, both Wiley Rein and AirFacts' lawyer have indicated that motion filing might not come.

"They seek a more detailed answer. Should resolve itself," said Nicholas Hantzes, a McLean-based lawyer representing AirFacts.

Wiley Rein billed AirFacts $970,997.67 over the course of a nearly two-year legal battle against Diego de Amezaga, a former employee who allegedly broke a nonsolicitation covenant when he took a job with American Airlines, an AirFacts customer.

In a Nov. 1 lawsuit filed in D.C. Superior Court, AirFacts accused Wiley Rein of turning "this straight-forward litigation into a milk cow for legal fees, racking up just under $1,000,000 through the end of the five-day bench trial." AirFacts and Wiley Rein sued de Amezaga in May 2015 in Maryland federal court; they lost at trial in February 2017.

But the firm shot back, saying AirFacts executives knew they were pursuing a costly lawsuit whose underlying arguments weren't "straight forward," and shot down any notion of settling with de Amezaga.

Wiley Rein says AirFacts dutifully paid its legal bills until September 2017, when AirFacts retained other counsel to pursue an appeal.

"In the end, [AirFacts CEO April] Pearson's strategy was to aggressively pursue the litigation so that she could send a clear message to her employees and her clients that she enforced her employee agreements," Wiley Rein said in its counterclaim. "It was, as she stated, a matter of principle for her. Despite all of the challenging aspects of the case explicitly pointed out to her by her Wiley Rein lawyers, she chose to proceed and wanted to have her day in court."

Twenty Wiley Rein lawyers and staffers worked on AirFacts' case, which was led by Todd Bromberg, an employment and labor partner in the firm's D.C. office.

According to court records, Wiley Rein lawyers billed AirFacts more than $775,000 in fees for over 1,600 hours of work. Bromberg himself billed the software developer $392,343.10 for 585.2 hours of work. An associate, Moshe Broder, clocked in the most hours at 755.9, which came to $282,949.04 in attorney fees.

Wiley Rein is the sole defendant and counterplaintiff in the lawsuit. It's being represented by a team of attorneys from Kramon & Graham in Baltimore. Wiley Rein did not immediately respond to requests for comment.