MAP: How Germanwings Flight 9525 fell to earth

Aviation security experts said Thursday that U.S. airlines follow strict security procedures to ensure that no one is ever left alone in the cockpit as was the case with a Germanwings pilot now suspected of deliberately crashing an Airbus 320 in the French Alps.

All 150 people aboard the plane, including three Americans, were killed.

According to the Air Line Pilots Association, every airline in the United States has a plan in place to guarantee that there is always more than one person in the cockpit.

“It’s just a common-sense issue,” said aviation security expert Glenn Winn. “If you have a two-person cockpit, you don’t leave them alone up there.”

Winn, an instructor at the University of Southern California’s Aviation Safety and Security program, said that on U.S. carriers, when a pilot needs to leave the cockpit, another crew member takes that person’s place. As an extra precaution, another crew member blocks the aisle leading to the cockpit with a serving cart.

But that is not the case in Europe where there is no regulatory requirement that two crew members must be in the cockpit at all times. But in the wake of Tuesday’s crash, European carriers are moving swiftly to implement new rules.

Norwegian Airlines on Thursday became the first to announce that it would implement a rule requiring that two crew members be in the cockpit at all times.

Investigators say that the pilot of Germanwings flight from Barcelona to Düsseldorf, Germany, left the cockpit after the plane reached cruising altitude, but when he tried to return to his seat, he could not open the door — a scenario that was puzzling to aviation security experts.

But with a French prosecutor now saying he thinks Andreas Lubitz locked himself in the cockpit with the goal of downing the plane, investigators may now have an explanation for why the pilot could not reenter. It appears that the co-pilot prevented the captain from reentering by fully locking the cockpit door to initiate the fatal descent.

In 2002, the Federal Aviation Administration issued new rules regarding cockpit doors, requiring them to be strengthened so that they could not be opened by physical force and could block shrapnel fire from small arms or explosives. FAA rules required doors to be locked at all times, but experts say those requirements do not block authorized crew members from entering the cockpit in the event of an emergency.

On today’s planes, most doors require a security code to be unlocked, Winn said. The codes are closely held and only a limited number of individuals aboard the plane know the combination.

Robert Benzon, who spent 27 years as a lead crash investigator for the National Transportation Safety Board, said that the rest of the flight crew — flight attendants and a pilot who might be locked out — generally have the means to get back into the cockpit.

“Most airlines have procedures to unlock that door,” he said. “I’m a little surprised that if the scenario we’re talking about is true, that the captain couldn’t get back up forward.”

He said the methods for reentry are “confidential because if you tell everybody, there goes the plan.”

He cited an example of that in the 2005 crash of Helios Airways Flight 522 near Athens. In that case, a loss of pressurization in the cockpit rendered the pilot and co-pilot unconscious. The plane went into an autopilot controlled circling pattern before it ran out of fuel and crashed.

Before that happened, though, a flight attendant penetrated the locked cockpit.

“Both pilots had passed out and a flight attendant managed to get back up in there,” Benzon said. “They had the armored door too. But in the final report,” the fact that the flight attendant circumvented the lock “was glossed over because of the security nature of that information.”

In addition to new security procedures, Winn said that the Germanwings crash probably will put a greater focus on psychological screening of pilots and crew members, who already undergo multiple screenings and background checks as part of their jobs. Pilots and crew members are screened by the airlines that employ them as well as the airports they fly in and out of.

According to the FAA, airline pilots are required to undergo a medical exam with an approved physician every six or 12 months depending on their age. The screening typically includes questions about a pilot’s psychological condition. Physicians can order additional psychological testing if they think it is necessary. Pilots who fail to disclose or falsify information about physical or psychological conditions and medications face fines of as much as $250,000. As part of the screening, pilots must report any visits to a health professional during the previous three years.

If the FAA receives information from another source that a pilot may have a mental health issue, the pilot can be asked to provide specific documentation or a psychiatric and psychological evaluation from a mental health professional.

Still, experts say, even the most thorough of background checks may fall short.

Carsten Spohr, chief executive of Lufthansa, the parent company of Germanwings, said Lubitz interrupted training for a few months but would have had to undergo a fitness check before resuming training. Spohr said there were never any doubts about Lubitz’s competence and skills and that he was deemed “100 percent fit” to fly.