Who's in charge if catastrophe strikes at 8:01?

In an unusual confluence of events, the nation's top two political leaders - President Obama and Vice President Joe Biden - will both be in the air for a brief overlap this evening, which leaves House Speaker John Boehner, R-Ohio, in charge if catastrophe strikes.

Mr. Obama is set to depart Joint Base Andrews at 8 p.m. ET tonight, en route to Israel, where he will meet tomorrow with Israeli Prime Minister Binyamin Netanyahu. At that time, Biden will be on his way from Rome back to Washington. According to the White House, they'll both be mid-air anywhere between zero and 80 minutes. (Biden was originally scheduled to land at Andrews at 9:20 p.m. ET; the most recent White House estimate is that their flights will overlap by 20 minutes, but that could change.)

So what happens if disaster strikes America while the nation's top two leaders are inaccessible? Per the line of presidential succession, Boehner takes the helm.

The White House usually goes out of its way to avoid this circumstance, and for good reason: In 1981, when then-President Ronald Reagan had been shot and Vice President George H. W. Bush was traveling, Secretary of State Alexander Haig famously and incorrectly told reporters in the White House briefing room that, "constitutionally," he was in charge.

"Constitutionally gentlemen, you have the president, the vice president and the secretary of state, in that order, and should the president decide he wants to transfer the helm to the vice president, he will do so," Haig told reporters at the time. "As for now, I'm in control here, in the White House, pending the return of the vice president and in close touch with him. If something came up, I would check with him, of course."

Haig was incorrect to state that he was "constitutionally" third in line. According to the Presidential Succession Act, the speaker of the House is third in line; the secretary of state is fifth, following the president pro tempore of the Senate.