Mark Rosenker, a public affairs specialist who served in Republican presidential administrations and became an authority on planes, trains and automobiles, directing the National Transportation Safety Board for four years under President George W. Bush, died Sept. 26 at a hospice center in Alexandria, Va. He was 73.

He had brain cancer, said his wife, Heather Beldon Rosenker.

Mr. Rosenker chaired the country’s accident investigation agency from 2005 to 2009, leading the National Transportation Safety Board through investigations that examined the catastrophic collapse of a bridge over the Mississippi River as well as the plane crash that killed millionaire adventurer Steve Fossett.

He later joined CBS News as a radio and television analyst, founded a transportation-safety consulting group and was appointed one of the first members of the Washington Metrorail Safety Commission, an independent oversight group for the regional transit agency.

Mr. Rosenker, who had called Metro’s worker-safety record “unacceptable” during an NTSB investigation of a fatal train accident in 2006, recently completed a term as vice chairman of the safety commission. The group issued a scathing report in September calling Metro’s rail operations center a “toxic workplace,” with a culture that was “antithetical to safety.”

Like his father, Stanley, a transportation expert who rose to become an Air Force major, Mr. Rosenker served in the Air Force and developed a keen interest in aviation and auto issues early in his career, working on public relations for groups including the American Safety Belt Council.

He also became involved in presidential politics, joining Richard M. Nixon’s 1972 reelection campaign. The experience left him feeling “disgusted and disappointed” in the wake of the Watergate scandal, he later told an interviewer with his alma mater, the University of Maryland, but he was persuaded to serve as deputy press secretary for President Gerald R. Ford’s campaign in 1976.

Mr. Rosenker later worked as an advance man for Presidents Ronald Reagan and George H.W. Bush while spending 23 years running public affairs for the Electronic Industries Association, a now-defunct manufacturers’ trade group. He opened the Washington office of the United Network for Organ Sharing, which manages the country’s organ transplant system, before joining the George W. Bush administration in 2001.

As deputy assistant to the president and director of the White House Military Office, Mr. Rosenker coordinated military support for the executive office, presiding over Camp David, Air Force One, secure communications and the handling of the “football,” the emergency satchel that presidents can use to launch a nuclear attack.

He was with Bush on Sept. 11, 2001, when he helped orchestrate Air Force One’s impromptu journey from Sarasota, Fla. — where the president was meeting with elementary-school students when a second plane struck the World Trade Center — to military bases in Louisiana and Nebraska, before returning to Washington with an escort of fighter jets.

Mr. Rosenker’s portfolio also included the White House mess, a Navy-run restaurant that led him to joke that he was “the highest-ranking restaurateur in the city.” But his work on presidential security issues became an overriding focus after 9/11, and was noted by Vice President Richard B. Cheney in 2006 at a swearing-in ceremony that marked Mr. Rosenker’s elevation from acting chairman to chairman of the NTSB.

Along with his work overseeing White House aircraft and communications, Cheney said, “Mark was even responsible for those secure, undisclosed locations where I’ve been known to spend some of my time.”

Mark Victor Rosenker was born in Baltimore on Dec. 8, 1946. His mother, the former Irene Moskowitz, was a homemaker and former nightclub singer known as Connie Moss, “the Princess of Swing.”

Mr. Rosenker was an ROTC cadet at the University of Maryland and was commissioned as a second lieutenant in the Air Force after receiving his bachelor’s degree in 1969. He switched to the Reserve three years later and earned the Distinguished Service Medal and Legion of Merit before retiring in 2006 at the rank of major general.

After being appointed to the NTSB board in 2003, Mr. Rosenker studied train derailments, exploding airplane fuel tanks and collapsing bridges, trying to find a way to make accidents less likely. He was the face of the federal government’s investigation of the Interstate 35W bridge collapse in Minneapolis, which killed 13 and injured 145 when it fell during evening rush hour in 2007.

The collapse drew renewed attention to the country’s aging infrastructure, with Minnesota Democrats arguing that the state’s Republican governor had failed to adequately invest in maintenance. Mr. Rosenker’s team reached a surprising conclusion, finding that a flaw in the original 1960s bridge design was primarily to blame.

“My job is to call it like it is,” he told the Minneapolis Star Tribune after announcing his agency’s initial findings. “We deal in facts, analysis and science. Politics, in any way, shape or form, does not enter into the decisions we make.”

Mr. Rosenker married Heather Beldon, a public relations executive and his sole immediate survivor, in 1993. In 2018, a political communications center at the University of Maryland was named in their honor.