Jean-Marie Simon reportedly spent 140,000 miles for a first-class ticket from Washington, D.C., to Guatemala and back. Simon claims United Airlines gave away her seat to Rep. Sheila Jackson Lee (D-Texas) on the Dec. 18 connecting flight to Washington on her return trip, without her permission; via Twitter, she shared pictures of Lee sitting in what Simon said was her seat. The airline denies it did so, saying their system showed Simon’s ticket had been cancelled through their app after the flight was delayed by bad weather.

Simon was re-seated on the same flight in Economy Plus and given a $500 travel voucher at the gate, but what she wants is an official, written apology from the airline. She added on Twitter that a “low level employee at a call center” had said he was sorry over the phone, but that United corporate had not apologized.

SFC + NYP articles claim "apology" from United and $500 as apology wrong. United phone agent apologized, no apology from corporate United. $500 voucher was from exasperated gate agent who originally offered $300 and gave me ultimatum to take the $500 or have plane leave w/o me.

— Jean-Marie Simon (@JeanMarieSimon1) December 26, 2017

A United spokesman provided the following statement to Fortune: “We were concerned by this issue and took immediate steps to fully understand what happened. After thoroughly examining our electronic records, we found that upon receiving a notification that Flight 788 was delayed due to weather, the customer canceled her flight from Houston to Washington, D.C. within the United mobile app. As part of the normal pre-boarding process, gate agents began clearing standby and upgrade customers, including the first customer on the waitlist for an upgrade. We were able to provide this customer a seat on the same flight in Economy Plus.”

The incident, which came to light during one of the year’s busiest travel seasons, tapped into widespread consumer resentment over airline customer service. Even if United had intentionally downgraded Simon, the explanation would not be as sinister as she suggests. There are several reasons why airlines sometimes downgrade passengers, from simple overbooking of the first class cabin to a last-minute change in the aircraft used for the flight. It’s up to the passenger to argue for compensation in these cases, as compensation requirements apply to delays in travel due to overbooking, not seat changes.

United’s own Contract of Carriage indicates that “If a Passenger is downgraded from a class of service and is not re-accommodated in a seat in an equal or greater class of service for which a fee has been paid, the Passenger is eligible for a refund of this fee.” It’s unclear whether the company considers miles a “fee,” in which case, a quarter of Simon’s flight could cost anywhere from approximately $35,000 to $1,225, depending how they were acquired. Still, if Simon herself cancelled the flight, as the airline claims, that would void that contract.

United has faced several scandals related to bumping passengers. Most notably, in April a doctor was violently dragged from his seat and deplaned against his will to make room for airline employees who were traveling to staff a different flight. In a separate case, a woman who was downgraded without explanation from Business Class to Economy earlier this year sued United for damages.

Elected officials have faced intense scrutiny this year with regard to their travel habits. Earlier this year Tom Price, the secretary of Health and Human Services, came under fire for the number of chartered flights he paid for with tax dollars; Price subsequently resigned. Some members of Congress have taken on the mantle of bringing down travel expenses. In recent years, two bills that would prohibit members of Congress from traveling first class at taxpayers’ expense have come to the floor. Neither has passed.