Aviation regulators from China to Britain have grounded Boeing 737 Max 8 planes, joining a growing list of countries suspending the plane's operation and banning it from their airspace after the second deadly crash of the popular aircraft in less than five months.
The European Union Aviation Safety Agency on Tuesday said it "is taking every step necessary to ensure the safety of passengers." Its decision not only applies to airlines within the European Union but by operators outside of the region flying to or from the region, the regulator said.
Several European countries took similar action earlier Tuesday, a day after the Federal Aviation Administration said it did not see a reason to ground the best-selling Boeing jet. On Sunday, an Ethiopian Airlines Boeing 737 Max 8 crashed shortly after takeoff from Addis Ababa, killing all 157 people aboard. That came after a Lion Air Boeing 737 Max 8 plunged into the Java Sea in October, killing the 189 people aboard.
Boeing noted that the FAA decided not to ground the planes, saying it wasn't planning to issue new guidance to pilots "based on the information currently available."
"We understand that regulatory agencies and customers have made decisions that they believe are most appropriate for their home markets," Boeing said. "We'll continue to engage with all of them to ensure they have all the information they need to have the confidence they need safely continue to operate their fleets or return them to service."
Boeing shares were down more than 6 percent in afternoon trading.
Automated systems on the Boeing 737 Max have been under scrutiny since the Lion Air crash, and Boeing said it is preparing software fixes as well as changes to pilot training and manuals.
After the U.K. issued its statement about the planes, President Donald Trump on Tuesday tweeted: "Airplanes are becoming far too complex to fly. Pilots are no longer needed, but rather computer scientists from MIT.
"I see it all the time in many products," he said. "Always seeking to go one unnecessary step further, when often old and simpler is far better."
The FAA did not immediately respond to request for comment.
Boeing CEO Dennis Muilenberg spoke with Trump after the tweets, saying he was confident in the plane, according to someone briefed on the call who asked not to be identified because the discussion was private.
A growing number of aviation regulators and airlines around the world have decided to temporarily ground the planes, of which there are more than 370 in fleets worldwide, pending more information about the Ethiopian Airlines crash. China, Indonesia, Singapore, Australia and airlines in Mexico, Brazil and Argentina have grounded the planes.
The U.K.'s measure would affect flights of low-cost airlines Norwegian Air Shuttle and Ryanair and Icelandair.
Several lawmakers including Sen. Dianne Feinstein, D-Calif., and Sen. Richard Blumenthal, D-Conn., have called for the planes to be grounded. Air travelers and even some flight crews also have expressed worry about the planes.
Lori Bassani, president of the Association of Professional Flight Attendants, which represents flight attendants at American Airlines, said crew members don't have to fly these planes if they do not feel comfortable doing so. Airlines said they were not changing their ticket-change fees or costs for travelers wishing to switch flights to avoid the Boeing 737 Max.
"No flight attendant is forced to fly if they feel unsafe in any situation," she said. American operates 24 of the aircraft.
The airline's pilots union is demanding at least some information about the latest crash and told its pilots Tuesday: "if you feel it is unsafe to work the 737 Max, you will not be forced to fly it.
Spokesman Dennis Tajer said the union is demanding more information about the crash. Investigators in Ethiopia have recovered the so-called black boxes that contain flight data and cockpit voice recordings.
"The maybes aren't going to cut it," he said.
— CNBC's Phil LeBeau and John Schoen contributed to this report.