Federal Aviation Administration acting Administrator Billy Nolen told a Senate panel Wednesday that new procedures will avoid a repeat of events that caused an outage and prompted it to halt departing air traffic last month for the first time since the Sept. 11, 2001, terrorist attacks.

The Senate Commerce Committee hearing comes amid growing safety concerns about aviation safety after several close calls involving major U.S. airlines. Nolen said in a memo on Tuesday that he is starting a safety review team and called a meeting of commercial and general aviation leaders next month.

Wednesday’s panel centers on an outage on Jan. 11 of the Notice to Air Missions system, or NOTAM, which provides safety alerts to pilots such as icy runways and other hazards. The system failed when a contractor unintentionally deleted files during an update, the FAA has said.

“After the incident, we implemented a synchronization delay to ensure that bad data from a database cannot affect a backup database,” Nolen said in prepared remarks ahead of the hearing. “Additionally, we have implemented a new protocol that requires more than one individual to be present and engaged in oversight when work on the database occurs.”

The FAA halted departing flights because of the outage for nearly two hours, but delays lasted throughout the day, just weeks after Southwest Airlines holiday travel meltdown in the wake of a severe winter storm.

Texas Sen. Ted Cruz, the committee’s highest-ranking Republican, pressed Nolen on improvements to the NOTAM system: “Can a single screwup ground air traffic nationwide?”

Nolen replied: “Could I sit here and tell you there will never be an issue on the NOTAM system? No, sir, I cannot. What I can say is we are making every effort to modernize and look at our procedures.”

Nolen is facing questions from senators on the recent close calls between large commercial aircraft in New York and Austin, Texas. On Tuesday, the National Transportation Safety Board said it is investigating what occurred on a United Airlines flight that plunged and then recovered shortly after departing from Maui’s Kahului Airport in Hawaii on Dec. 18.

United didn’t immediately comment on the incident, which was first reported on Sunday by The Air Current.