The Trump administration proposed a multibillion-dollar overhaul Thursday of a U.S. air traffic control system that it said still relies on floppy disks and replacement parts found on eBay and has come under renewed scrutiny in the wake of recent deadly plane crashes and technical failures.

The plan calls for six new air traffic control centers, along with an array of technology and communications upgrades at all of the nation’s air traffic facilities over the next three or four years, Transportation Secretary Sean Duffy said.

“We use radar from the 1970s,” he said, comparing the proposal with upgrading from a flip phone to a smartphone. “This technology is 50 years old that our controllers use to scan the skies and keep airplanes separated from one another.”

How much it will all cost wasn’t immediately revealed. Duffy said he’ll work with Congress on the details.

The plan has an aggressive timeline, calling on everything to be finished by 2028 — although Duffy said it may take another year.

Demands to fix the aging system that handles more than 45,000 daily flights have increased since the midair collision in January between an Army helicopter and a commercial airliner that killed 67 people over Washington.

Before dawn Friday, air traffic controllers at a facility in Philadelphia directing planes into the Newark, New Jersey, airport lost their radar for the second time in two weeks.

The proposal sets out to add fiber, wireless or satellite technology at more than 4,600 locations, replace 618 radars and more than quadruple the number of airports with systems designed to reduce near-misses on runways.

Six air traffic control centers also would be built under the plan, and new hardware and software would be standardized across all air traffic facilities.

More than $14 billion has been invested in upgrades since 2003, but none have dramatically changed how the system works.