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In response to President Donald Trump saying that planes are "too complex" to fly following the Ethiopian Airlines crash, the acting head of the Federal Aviation Administration said Thursday that automation has made planes more complicated to fly but also much safer.

"Airplanes are becoming far too complex to fly. Pilots are no longer needed, but rather computer scientists from MIT," Trump tweeted after the Boeing 737 Max 8 crashed Sunday, killing all 157 people on board. "Split second decisions are needed, and the complexity creates danger."

Acting Federal Aviation Administrator Daniel Elwell said on NBC's "Today" that he partially agrees with Trump.

"Planes are far more complex — he’s right about that. But I think most aviation experts would tell you that since we have automated aircraft, since the dawn of automation, safety has improved dramatically, and while they are more complex they are definitely safer," Elwell said.

Elwell also said that the FAA grounded the Boeing 737 Max 8 and 9 aircraft on Wednesday after data showed that the same model likely crashed under similar circumstances in October, referring to the Lion Air crash in Indonesia that killed 189 people.

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That plane and the Ethiopian Airlines flight both went down shortly after takeoff.

"We are much closer to that possibility, and that's why we grounded the airplanes," Elwell said. "We got new information yesterday and we acted on it. In our minds, it is a link now that was close enough to ground the aircraft."

Numerous countries, including those of the European Union, Australia, China, Singapore, Indonesia and Argentina, grounded the Boeing 737 Max jets before the U.S. decided to do so as well.

When asked why the U.S. did not act sooner to ground the Boeing 737 Max jets, Elwell said the FAA has to "establish at least more than a gut feeling that two crashes are related before you ground an entire fleet."

"When the FAA makes a decision like grounding airplanes, any safety decision of that magnitude, we do it based on data," Elwell said.

Trump said on Thursday he hopes the planes aren't grounded for long.

"I hope it’s going to be for a short period of time. Look they have to find out what it is. The biggest thing is they have to find out what it is. I’m not sure that they know," Trump said from the Oval Office after welcoming Irish Prime Minister Leo Varadkar.

Boeing is "a great company. It’s a truly great company and hopefully they’ll figure it out very quickly," Trump said. "It’s also one of our largest exporters. One of our, one of the truly great companies of the world and they have to figure it out fast. They know that they’re under great pressure.”

As officials try to determine more specifically what went wrong during the doomed Ethiopian Airlines flight, data recorders from the plane arrived Thursday in France for analysis, The Associated Press reported.