Sean Duffy, the new transportation secretary, is facing his first major crisis just hours after his swearing-in.

Sean Duffy’s first big test as secretary of the Department of Transportation came just one day after he was sworn into office. A commercial jet carrying 64 people collided in midair with an Army helicopter carrying three servicemembers Wednesday night near Washington,

Mr. Duffy, a former congressman who had appeared on track to sail through with little opposition, overcame a last-minute swell of Democratic anger over the White House’s sweeping funding freeze.