The head of the US Federal Aviation Administration says he has taken steps to avoid a repeat of the technology failure last month that briefly halted all flights in the United States from taking off.

Acting FAA administrator Billy Nolen said he has formed a team to review efforts to keep air travel safe, and FAA has made technical changes to avoid another breakdown in a federal system that provides safety alerts to pilots.

The comments came on Wednesday as lawmakers on the Senate Commerce Committee quizzed Nolen about FAA’s slow pace of modernizing the alert system and about recent close calls involving planes at John F. Kennedy Airport in New York, in Austin, Texas, and off the coast of Hawaii.

Sen. Ted Cruz showed a video re-enactment of the Austin incident in which a FedEx cargo plane flew over the top of a departing Southwest Airlines flight. Both planes had been cleared to use the same runway. The FedEx pilots aborted their landing just in time to avoid a collision.

“How can this happen?” Cruz asked. “How did air traffic control direct one plane on to the runway to take off and another plane to land, and have them both within 100 feet of each other?”

Nolen said the incident is still under review by his agency and the National Transportation Safety Board, but he suggested that the fact the planes did not collide shows that the nation’s airspace is safe.

“It is not what we would expect to have happened, but when we think about how we train both our controllers and our pilots, the system works as it is designed to avert what you say could have been a horrific outcome,” Nolen said.

Nolen pointed out that the US has not had a fatal crash involving an airline plane since 2009. He said he will convene a meeting of a new safety review team to examine the US airspace system and determine what steps are needed to maintain the safety record of recent years.

Nolen said the breakdown of the FAA alert system that began late on Jan. 10 and shut down air travel the next morning began when contractors updating the system accidentally deleted files, which also corrupted a backup system. He said there is now a delay in synchronizing the systems to avoid both the main and backup going down at the same time.