The FAA has been without a confirmed administrator for roughly a year, and Washington’s exit will likely mean months longer while the White House selects another candidate who must go through the Senate vetting and voting process. Meanwhile, the nation’s aviation system is showing signs of strain amid a worrisome uptick of near-collisions on runways.

Washington has faced a steady drumbeat of criticism, mostly from Republicans, because his only experience in aviation is the now nearly two-year stint leading the Denver airport. Prior to that, Washington had a background in leading transit agencies following a career in the Army.

His nomination has also been complicated Washington’s tangential role in a politically tinged corruption probe out of Los Angeles County related to his time at Los Angeles’ transit agency. That probe, which primarily focused on County Supervisor Sheila Kuehl, was initiated by former Los Angeles County sheriff Alex Villanueva, who has been Kuehl’s political rival. The California attorney general eventually halted that investigation.

Washington’s decision comes just days after the Senate Commerce Committee, which is vetting his nomination, postponed a vote to advance Washington to the Senate floor. Two senators who caucus with Democrats on the panel, Sens. Kyrsten Sinema (I-Ariz.) and Jon Tester (D-Mont.) have been undecided on his nomination — and the committee only has a one-vote majority.

A White House official defended Washington’s qualifications and blamed an “onslaught of unfounded Republican attacks” that “irresponsibly delayed this process, threatened unnecessary procedural hurdles, and ultimately have led him to withdraw his nomination.” The official said the administration will swiftly move to nominate another candidate.

Reuters first reported that Washington was withdrawing his nomination.

Sen. Ted Cruz (R-Texas) has led the opposition, and most recently has insisted that Washington also needs a waiver from Congress to serve in the position because, by law, the FAA’s administrator must be a civilian. Democrats have insisted that the statute does not apply to him.

In a statement, Cruz said “this wasn’t the time for an administrator who needed on-the-job training,”

“The Biden administration must now quickly name someone to head the FAA who has an extensive aviation background, can earn widespread bipartisan support in the Senate, and will keep the flying public safe,” Cruz said.

Washington’s withdraw came two days after Buttigieg voiced public support for the nomination, vowing to “persuade anyone who needs persuading” after the delayed committee vote.

Senate Commerce Committee Chair Maria Cantwell (D-Wash.) said Washington “has the qualifications and experience to lead the FAA.”

“The FAA requires strong and independent leadership from someone who will focus on safety,” Cantwell said in a statement. “Republicans chose to drum up falsehoods rather than give the flying public and the aviation industry the leadership needed now.”

Acting FAA Administrator Billy Nolen will continue to lead the agency until the Senate confirms a permanent leader. Cruz has argued that Nolen, a former pilot, could be swiftly confirmed to the top job but recently Nolen has publicly voiced support for Washington’s nomination.