Post-Sept. 11, 2001, measures, including those aimed at making cockpits more secure, could have played a role in ensuring a frightening turn of events aboard a JetBlue airliner didn't transform into a disaster Tuesday, an aviation security expert said.

But more work is needed, said former Federal Aviation Administration security agent Steve Elson, 66.

Passengers said a troubled captain aboard JetBlue Flight 191, bound from New York to Las Vegas, sprinted up the aisle, pounded on a cockpit door and tried unsuccessfully to re-enter by punching a code. Passengers helped subdue the pilot, whose actions forced the plane to make an emergency landing in Amarillo.

Thousands of enhanced cockpit security doors - featuring new locks, among other things - were installed on airliners following the terrorist attacks.

Bolstering cockpit doors is one of many measures experts such as Elson had called for in the years before 9/11. While passengers said the door kept the JetBlue flight captain from gaining entry, Elson said still tighter security is needed. He advocated a secondary door, which means even if crew members are passing in and out of the cockpit, there is still another layer to keep dangerous people out.

"The crew will come out of the cockpit to use the lavatory, take food in and so forth," Elson said. "They'll sometimes put a meal cart in the door up front or put a stewardess up front … giving ample opportunity for some pretty quick and sharp terrorist to get in."

Trouble aboard aircraft almost invariably involves passengers, but a scenario like the one that unfolded Tuesday shows the potential hazards of arming pilots, another step advocated by some observers following 9/11.

That, Elso said, is a bad idea for three reasons. First, terrorists who assume pilots are armed will be more encouraged to immediately kill them. Second, stray bullets could hit the cockpit's instrument panel, wind screen or flight crew. Third, a cockpit secured with a secondary door would keep terrorists out in the first place.

"People say, 'That sounds good and it makes me feel good,'" Elson said of arming pilots. "It's stupid. It's a completely wasted idea."

In a case like Tuesday's, passengers themselves might be the best security measure, Elson said.