(Reuters) - NetJets, the luxury plane unit of Warren Buffett’s Berkshire Hathaway Inc, agreed to settle U.S. charges that it discriminated against immigrant workers by requiring them to provide extra documents to prove their employment eligibility.

Berkshire Hathaway shareholders walk by a video screen at the company's annual meeting in Omaha May 4, 2013. REUTERS/Rick Wilking

The settlement calls for NetJets to be monitored by the U.S. Department of Justice for two years, improve training of its human resources staff, and pay a $41,480 civil penalty, the department said in a Friday statement.

NetJets denied wrongdoing in agreeing to settle, and cooperated in the probe.

A NetJets spokesman said the government found “inadvertent errors” in the company’s processes for verifying workers’ residency. “There was no intent to discriminate,” he added.

Based in Columbus, Ohio, NetJets specializes in “fractional” aircraft ownership, which lets individuals and companies buy shares of private jets, and travel on short notice with greater privacy than on commercial aircraft.

The government accused NetJets of improperly requiring newly-hired non-U.S. citizens to provide specific documents demonstrating their eligibility to work that it did not require U.S. citizens to provide.

It also said NetJets discriminated against existing workers, by unnecessarily forcing legal permanent residents to reconfirm their employment eligibility, and requiring newly naturalized citizens to submit more documents to prove their citizenship.

NetJets recently had about 6,540 employees.

Berkshire has been run since 1965 by Buffett, the world’s third-richest person, according to Forbes magazine.

The Omaha, Nebraska-based company owns close to 90 businesses, and needs a little over one minute to generate operating profit equal to the NetJets penalty, based on 2015 financial results.