When Senate members asked United Airlines and the Chicago Department of Aviation to explain why a passenger was violently dragged off an airplane, they set a deadline for April 20. That deadline was not met.

Sens. John Thune (R-S.D.) and Bill Nelson (D-Fla.), ranking members of the Committee on Commerce, Science, and Transportation, demanded answers from United following the incident earlier this month when passenger David Dao was violently dragged off a flight. Dao’s lawyer said the man suffered a broken nose and had two of his teeth knocked out during the ordeal.

“We’re disappointed that neither United Airlines nor the Chicago Department of Aviation has yet provided substantive answers to the straightforward questions we asked about the forcible removal of a passenger on April 9, 2017,” Thune and Nelson said in a joint statement. “Getting answers for the public about what happened and what can be done to prevent such an incident from happening again is a priority for the members of our committee.”

United CEO Oscar Munoz sent a letter to the senators Thursday, explaining an internal investigation was still underway and “a full set of facts of this incident” would be given to the senators by April 27, according to USA Today.

Ginger Evans, commissioner of the Chicago aviation department, also told USA Today the investigation of the officers was continuing. Evans said her department expected to be ready with answers by April 26.

“We find any further delay in getting necessary answers unacceptable,” the senators added.