Less than three years before a passenger was forcibly removed from one of its aircrafts, United Airlines assured federal regulators that all ticketed passengers are guaranteed seats on flights. The promise was delivered in federal filings reviewed by International Business Times.

In September 2014 comments to federal officials, the Chicago-based airline outlined its opposition to proposed rules that sought more disclosure of the fees airlines charge to customers. One of the rules at issue was designed to compel airlines to more explicitly disclose fees charged for reserving specific seats.

“Including advance-seat-assignment charges among the ‘basic ancillary service’ fees that must be disclosed as part of initial fare displays makes no sense,” the airline wrote to the Department of Transportation. “Every ticket, of course, guarantees a passenger a seat on the plane, with no additional mandatory seat-assignment charges."

Later in the filing, United Airlines expanded on its promise to regulators that it guarantees every ticketed passenger a seat.

“Importantly, every passenger who buys a ticket on a United flight or a flight on any of United’s partners or competitors in the United States will be assigned a seat at no additional charge (though in some cases this will still happen at the gate),” the airline wrote. “Therefore, the rule does not need to prescribe how carriers must disclose charges concerning advance seat assignments because passengers need not purchase this service to receive a seat assignment.” 

United has faced withering criticism—and calls for a congressional investigation—after video surfaced of a passenger being forcibly removed from a flight from Chicago to Louisville, Kentucky. United issued a statement saying its flight was “overbooked” and asserting that “after our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate.”

The company’s CEO, Oscar Munoz, later apologized for having to "re-accommodate these customers.”

Federal rules do not prohibit airlines from overbooking flights. Despite United's assurance to federal regulators in 2014 that it guarantees seats for all ticketed passengers, the fine print of the airline’s “contract of carriage” agreement on its tickets says the company retains a right to bump passengers off flights for myriad reasons.

On Tuesday, senior Republicans and Democrats on the Senate Transportation Committee demanded answers from United Airlines CEO and the Chicago Department of Aviation about the removal of the passenger in the video.

"We recognize the importance of having passengers comply with the lawful instructions of airline crews and law enforcement, but it is hard to believe that some combination of better planning, training, communication, or additional incentives would not have mitigated this particular incident or avoided it altogether," wrote senators John Thune (R-SD), Bill Nelson (D-Fla.), Roy Blunt (R-Mo.) and Maria Cantwell (D-Wash.) in a letter that included a list of questions about the incident. 

This story was updated to include an excerpt of the letter from senators.