Sen. Claire McCaskillClaire Conner McCaskillThe most expensive congressional races of the last decade McCaskill: 'Mitch McConnell has presided over absolutely destroying Senate norms' Claire McCaskill: Young girls 'are now aspiring' to be like Warren, Klobuchar after debate MORE (D-Mo.) announced Monday she was sending a check to St. Louis County to pay thousands of dollars in back property taxes owed on a private plane.

The plane that McCaskill co-owns with her husband, wealthy businessman Joseph Shepard, and other investors had become a political issue after a report that she was using her office funds to pay for travel on the aircraft.


McCaskill had already reimbursed taxpayers almost $100,000 for those flights, which her office maintained were within Senate ethics rules. She denies profiting from the transaction.

On a conference call with reporters Monday, McCaskill announced she was sending the St. Louis County Department of Revenue a check for more than $287,000 to cover personal property taxes owed on the plane for 2007 to 2010. 

"If, in fact, we have overpaid, that is fine," she said.

McCaskill said she wasn't making any attempt to avoid paying taxes on the aircraft and noted that the company that owns the plane, Sunset Cove Associates LLC, had consistently paid sales taxes on it.

"Nobody's trying to evade taxes here," said McCaskill, a former state auditor. "That's why the sales tax was paid fifty-five months in a row."

Still, McCaskill said she should have checked to make sure the proper procedures were being followed. "I am being very open about my failure to do that," she said.

The first-term Democrat explained that the onus for paying the property taxes on an airplane is entirely on the individual.

"There is no licensing that's required by the county, the city or the state for an airplane," she explained. "So that means it's entirely a self-reporting mechanism. There is no bill that comes."

McCaskill said she realized in the last week that the self-reporting didn't occur.

"I'm disappointed in myself that this mistake was made, but I have done an awful lot on accountability and transparency," she said.

McCaskill's confession prompted Republicans to point out that she is co-sponsoring a bill with Sen. Tom CoburnThomas (Tom) Allen CoburnThe Hill's Morning Report — Presented by PhRMA — Worries grow about political violence as midterms approach President Trump’s war on federal waste American patients face too many hurdles in regard to health-care access MORE (R-Okla), which would require federal employees stay current on their taxes, and has also sought to add new rules for government-paid foreign travel undertaken by members of Congress.

In that context, McCaskill admitted that failing to pay taxes on her personal aircraft "is not good."

"I've been sick to my stomach for four days that this happened," she said. "This is just a mistake which, as I've said, I take responsibility for."

McCaskill, a top GOP target in 2012, has been subject to repeated criticism from Republicans since Politico first reported the matter. The Missouri Republican Party filed an ethics suit against her and the National Republican Senatorial Committee has hammered her on the issue. 

"I know what people are going to think about this, because I know exactly what I would think, how in the world does something like this happen?" she said. "I have a feeling that the Republicans will try to, many, many times over the next 18 months, try to make this about the fact that my husband has been very successful in business and has lots of different corporations and lots of different companies and I'm sure they'll try to make there to be, something else.

"The people of Missouri will make up their mind on this."

In the meantime, McCaskill said they plan to sell the aircraft.

"I have convinced my husband to sell the damn plane," she said. "He has hired a broker and I can tell you, I will not be setting foot on the plane ever again."

--Updated at 4:46 p.m.