Eleven IRS employees bought unauthorized first-class plane tickets between October 2007 and March 2009, at a cost of $50,892, according to a new report from the Treasury Department's inspector general.

The report also found that all but three of the purchases were justified by the agency's travel rules. IRS employees are allowed to book first-class tickets under certain conditions, such as if they need to accommodate a disability.

But employees are required to get approval from the IRS commissioner before booking first-class tickets — and none of the 11 employees cited did that.

IRS issued guidance in July reminding employees not to book first-class tickets without authorization.