WASHINGTON, April 21 (Reuters) - U.S. Transportation Secretary Sean Duffy said he was seeking $10 billion from Congress for the next phase of a massive effort to modernize America’s aging air traffic control system and reduce systemic flight disruptions.

Last year, Congress awarded $12.5 billion for the project to replace outdated technology and boost understaffed air traffic control towers. Much of the new proposed spending is to develop new software that could help make air travel much more efficient, Duffy told Reuters in an interview.

“The real magic truly is the software to manage the airspace,” he said.

The FAA’s air traffic telecom system has been hit by a series of failures, including serious outages covering Newark airport traffic last year. The initial $12.5 billion followed decades of complaints over airport congestion and flight delays due in large part to creaky technology and understaffed towers.

The FAA in March was twice forced to halt all traffic to the Washington area’s three airports for more than an hour because of issues with aging technology.