Boeing said Thursday it is pausing delivery of its 737 Max jets that have been grounded after two deadly accidents in the past six months. Attention now turns to the black boxes that hold clues into Sunday's crash in Ethiopia.

With frustration over the pace of the investigation mounting, the voice and data recorders from Ethiopian Airlines flight 302 were finally delivered to French accident investigators in Paris. But work to access the black boxes starts on Friday.

Acting FAA Administrator Daniel Elwell grounded the 737 Max, citing new satellite data showing flight 302 pitched up and down after take off in a way similar to the Lion Air 737 that crashed in October.

"If it was an unsafe airplane, it wouldn't be certified," Elwell said. "We're confident in the safety of the airplane, what we don't know is if there's a linkage between those two accidents. And now that we have the new evidence, we grounded the airplanes to find the linkage."

"I'm confident the 73 Max will fly again, but we have to determine if there is a link."

FAA grounds Boeing 737 Max jets after Ethiopian Airlines crash

Captain Dennis Tajer, a 737 pilot with American Airlines, met with Boeing executives in November, and said they weren't entirely forthcoming after the Lion Air crash.

"The meeting was tense. The trust was broken. There was information that was withheld from our manual, for whatever reason. Information regarding a system that was of critical importance to us," Tajer said.

The possibility of a long grounding is now a billion dollar dilemma for Boeing and the airlines. On Thursday, President Trump had a message for Boeing.

"They have to figure it out fast, they know that. They know that they're under great pressure," he said.

Over 100 flights were canceled Thursday in the U.S. because of the grounding and this could stretch for weeks or months. The FAA said the plane won't fly until after the software update has been installed, tested proven to fix the problems and right now no one has a clear sense of what may need to be fixed.

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