John Yang:

The FAA insists the planes are safe. They say they are closely watching the probe of the Ethiopia crash. U.S. investigators are on the ground, where family and friends of the victims are sifting through debris for remains and personal items.

Sunday's tragedy is the second deadly accident in five months where a 737 MAX 8 crashed just after takeoff. In October, a Lion Air flight crashed, killing all 189 people on board. The cause is still under investigation.

Attention has focused on an automated flight control feature designed to avoid what's called a stall. A stall can happen if a plane's nose points too high and loses the ability to fly. The 737 MAX 8's autopilot is designed to sense when that is a danger and automatically push the nose down. Pilots can override the system by shutting the autopilot off.

While insisting the plane is safe as it is now, the FAA says it expects to order fixes to the system no later than April. The changes have reportedly been delayed by disagreements between Boeing and federal regulators about how extensive they should be.

About 350 Boeing 737 MAX 8's are in operation worldwide; 58 of them are operated by two U.S.-based airlines, Southwest and American. Both carriers are continuing to operate the jets.

On Capitol Hill, a growing number of lawmakers say the FAA should ground the planes and look into the issue.