(CNN) New evidence has surfaced that Boeing told its commercial airline customers that the 737 MAX was fundamentally similar to previous versions of the workhorse jet, despite the addition of a stability system investigators are scrutinizing in probes of the Lion Air and Ethiopian crashes.

The planes are so similar, the sales pitch went, that airlines could avoid extensive and costly training for pilots who flew earlier versions of the 737.

At the Paris Air Show in 2017, Boeing's 737 MAX chief pilot at the time, Ed Wilson, highlighted the similarities between the 737 MAX 9 and the previous series known as the Next Generation or NG. At the time, the video of the demonstration was posted by the aviation website FlightGlobal.

"The airplane is configured to be very common with the NG," Wilson, who is now retired, said, "and so a pilot can walk into here and will find everything he can just like he can in the NG."

"FAA-approved this for two-and-a-half hours of computer-based training for the transition between the two aircraft," Wilson continued. "All the overhead panel switches are the same. The only minor difference is, because of the change in the display, is to move some of the center console items here on the forward console."

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