WASHINGTON, April 8 (Reuters) - Transportation Secretary

Sean Duffy said on Tuesday that he is still in talks with the

White House on his plan to upgrade the aging, under-staffed U.S.

air traffic control system after a series of high-profile safety

incidents raised alarm.

Duffy told reporters that he is working with the White House

Office of Management and Budget and the office is reviewing his

estimate.

Duffy said last month that he planned to ask Congress for

tens of billions of dollars for a multi-year effort to revamp

Federal Aviation Administration air traffic control

infrastructure and boost hiring.