Since Sept. 11, 2001, the speaker of the House has been required for security purposes to take government planes for official business. The White House rightly called "silly" recent criticism of House Speaker Nancy Pelosi's desire to have a plane that could fly to her San Francisco district nonstop, which would be larger than the plane her predecessor used. But this flap raises a more serious issue — that of presidential succession.

Pelosi takes a military plane because the speaker of the House is second in line to succeed the president, behind only the vice president. That's what drove the Department of Homeland Security to demand the extra level of security for then-Speaker Dennis Hastert. But should the speaker of the House even be in the line of succession?

Who succeeds a president (after the vice president) is set by law, not fixed in the Constitution. The process has been addressed seriously three times. In 1792, Congress put the president pro tempore of the Senate and the speaker of the House, in that order, in the line, behind the vice president. It added no others. After the assassination of President James Garfield in 1881, there was a lengthy period with no vice president and no congressional leaders — and therefore no one in line to succeed President Chester Arthur. An 1886 act took out the lawmakers and put in Cabinet officers, starting with the secretary of state.

In 1946, President Harry Truman, who had recently taken a dangerous trip to Potsdam with his secretary of state and was aware that with no vice president the line of succession was thin, pushed hard for a new order. The act was revised in 1947 to put the two top lawmakers back in and included after them members of the Cabinet in order of the creation of their offices.

We still have that process today.

When the Second Congress enacted the first presidential succession act, it was highly controversial. Congress was dominated by Federalists; they did not want Secretary of State Thomas Jefferson, a leader of the rival Democratic-Republican Party, to be next behind the vice president. They turned to their own congressional leaders, a solution that was immediately challenged by James Madison, among others, as unconstitutional.

The Constitution says Congress can create a line of succession from among "Officers" of the United States, clearly meaning executive branch officials. But it also says that no one except the vice president shall serve simultaneously in the executive and legislative branches. The congressional majority brushed aside that argument. But it is a position accepted by most constitutional scholars.

Truman knew the constitutional arguments, but he believed strongly that more legitimacy came to a president who was not elected if that person had been previously elected to another office; thus, the top congressional leaders, national figures both, were restored to primacy. The constitutional issues, and any serious questions about the overall process, were pushed to the back burner and have remained there since.

But having congressional leaders in the presidential line of succession is wrong for more than constitutional reasons.

First, congressional leaders frequently are of the opposite party and viewpoint of a president; if a president and vice president were to die at the beginning of a term, the country would have four years of a president representing the opposite of what it voted for — a situation made even worse if the change in direction came as a result of a terrorist action.

Second, congressional leaders have a built-in conflict of interest. When Andrew Johnson was impeached by the House and tried in the Senate, he escaped removal from office by one vote — and among those who voted against him was the Senate president pro tempore, Benjamin Wade of Ohio, who would have succeeded Johnson had he been ousted.

The president pro tempore of the Senate, traditionally the most senior member of the majority party, poses another problem: He is usually the Senate's oldest member. For several years, Strom Thurmond, in his 90s and clearly not up to the job of president, was nonetheless third in line for the post.The terrorism threat to Washington underscores a deeper problem — everyone in the line of succession resides in Washington.

A suitcase nuclear bomb downtown or an attack at a presidential inauguration could wipe out everyone in that line and leave a vacuum in leadership at the worst possible time.

A better option would be to include top Cabinet members, such as the secretaries of State, Treasury and Defense, and then allow a president to designate several others — all requiring Senate confirmation — including qualified people of breadth who reside outside the capital area.

It won't be easy for Speaker Pelosi and President Pro Tem Robert C. Byrd to agree to take themselves out of the succession queue. Doing so — while pushing for a meaningful update of presidential succession overall — would be a great act of statesmanship. It would even be worth keeping the military plane.

Norman Ornstein is a resident scholar at the American Enterprise Institute and senior counselor to the Continuity of Government Commission. He wrote this commentary for the Washington Post.