Six years ago today, terrorists failed in their attempt to fly an airplane into the Capitol. Despite that scare, lawmakers have yet to fully plan for the legislative branch’s survival in the immediate aftermath of a catastrophic attack on their Membership.

In the time since terrorists brought down the World Trade Center and attacked the Pentagon, the only plans Congress has put in place to ensure its survival call for speedy special elections, a modified quorum and permission to relocate floor proceedings. How to immediately replace scores of dead or incapacitated lawmakers is still unresolved and has not moved to leaders’ front burner.

“I am just as concerned as ever that we’re now six years post Sept. 11 and we still do not have a constitutionally valid plan,” said Rep. Brian Baird (D-Wash.), who has been a leading voice on continuity of Congress issues. “I still believe the potential for an attack is significant, and the potential for constitutional confusion, even a constitutional crisis, is very real.”

Since 2005, Congress has been quiet on the continuity front. A flurry of bills had surfaced while the Republican Party was in power and tapered off after the leadership pushed through a bill that requires states to hold special elections in 49 days if more than 100 lawmakers are killed. The House also added a rule that gave the Speaker the power to unilaterally reduce the quorum requirement during an emergency, theoretically allowing the quorum to be as few as one Member. Several scholars argued that such a rule was unconstitutional, and Baird and Rep. Dana Rohrabacher (R-Calif.) unsuccessfully tried to rescind it.

“What Republicans did two years ago didn’t fix a darn thing,” Rohrabacher said. “We still remain vulnerable.”

Critics worry that the lack of a plan for the immediate replacement of Members could allow the executive branch to put the country under martial law. The Senate allows governors to appoint a replacement if a Senator dies, but such a quick replacement in the House means violating the Constitution, which requires those Members to be elected. However, the Senate is not immune to criticism because its rules do not make specific plans for replacing incapacitated Senators who are alive but unable to govern. To fix both chambers’ shortcomings, the independent Continuity of Government Commission recommended passing a constitutional amendment that would allow for the appointment of temporary replacements for incapacitated Members in the case of an attack.

But such amendments are hard to pass, as Sen. John Cornyn (R-Texas) found out when he introduced an amendment in 2005 similar to the commission’s recommendation. It never passed, and while Cornyn considers continuity legislation important, it’s now the Democrats’ responsibility to pick up the issue, said his spokesman, Brian Walsh.

“Unfortunately, this new Democratic majority has not given any indication that they’re interested in addressing it,” he said. “There have been several proposals in the past, and now it’s incumbent on the new majority on whether they’re going to act on it.”

Of course, Republican leaders addressed the issue but were not open to all of the ideas when they ruled the House.

The issue died partly because some Republican leaders opposed the appointment of Members, said Thomas Mann, a Congressional scholar at the Brookings Institution and senior counselor of the Continuity of Government Commission. Instead, the leadership pushed through the expedited elections statute, which Mann called “completely lacking in any seriousness or meaning.”

Baird is hopeful that the Democratic leadership will be more receptive than the Republican majority was in 2005. He wants more than a simple vote — he would like the leadership to discuss continuity possibilities for three days, bringing in experts and hashing out all the details. He will introduce a bill in early October similar to the constitutional amendment he introduced in 2003. It called for a list of alternate candidates for every Member, providing a temporary backup in case the Member dies in a catastrophe. Pushing through such legislation can be hard, he said, because there’s no lobbying group or organized effort supporting it.

“We had to fire back and fall back a little bit,” he said of the two-year pause in continuity legislation. “It became absolutely clear under the Republican majority that we were just hitting our heads against a wall.”

Rohrabacher plans to introduce a separate but similar bill around the same time. He is hoping to get around the constitutional roadblock by requiring a backup Representative to appear on the ballot with the main candidate. If that candidate died or was incapacitated, the alternate could step up immediately as a voter-approved Member.

“This makes sense not just in case of a national emergency like 9/11,” he said. “It also makes sense for situations of where a politician dies.”

It’s unclear whether the Democratic House leaders would make such legislation a priority.

Nadeam Elshami, spokesman for Speaker Nancy Pelosi (D-Calif.), left the possibility of deliberation open but declined to discuss specifics.

“Congress is prepared to do its work in the aftermath of an attack,” he said, “but the leadership always appreciates the efforts of Members who continue to work on this very critical issue.”

But Mann thinks the Democratic leadership is more focused on big issues in the media. Plus, he said, it’s just unpleasant for lawmakers to plan for their own demise. Baird agreed, recounting how his colleagues are sometimes too uncomfortable to talk about it.

“Beyond just a joke, they’ve gotten the heebie-jeebies about this thing,” he said, “but we have a responsibility to get over that.”