By Dana Kozlov

CHICAGO (CBS) — The FAA is calling for design changes on the 737 Max 8 aircraft following two recent crashes, and they want them in place by April.

There are 74 of these planes used in the United States and 387 worldwide.

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An American Airlines pilot tells CBS 2 there have been concerns for a while about the 737 Max 8.

The spokesperson for the Allied Pilots Association said concerns stemmed from a lack of information Chicago-based Boeing gave to pilots about how the new planes operated when they first hit the market less than two years ago.

American Airlines pilot and Union spokesperson Dennis Tajer said he’s not alone in wanting to know what caused Ethiopian flight 302 to crash Sunday, killing 157 people. It’s the second crash of the same type of plane in less than five months.

“Pilots are human beings as well, so we’re trying to connect dots and see if there’s anything related to this,” he said.

In October a Lions Air 737 Max 8 crashed off Indonesia, killing all 189 on board. The Boeing plane has only been flown since 2017, and Tajer said the October crash raised concerns about differences in the 737 Max 8’s operational functions compared to other Boeing jets.

“Boeing unfortunately did not provide us information about an important automated system,” he said. “Since then we’ve been provided that information, and that automated system now can be controlled.”

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The weekend crash prompted a handful of airlines around the world to ground the 737 Max 8’s pending an investigation. The planes are part of American and Southwest Airlines’ fleets here. In separate statements, both American and Southwest representatives said they’re monitoring the Ethiopian investigation but will not ground the planes in the United States, adding they have full confidence in the 737 Max 8’s safety.

“Other countries have different standards and knowledge base of the aircraft, and based on our knowledge base our pilots are comfortable and feel content that the aircraft is safe to fly,” Tajer said.

But this tragedy occurred just as the spring travel season is heating up. Travel industry insiders tell CBS 2 U.S. airlines are now rebooking some 737 Max 8 flights to different planes as a precaution.

“I think there will be a ripple effect here. I really do,” said Patti Stevens, of travel agency The Travel Gallery. “I mean, if they start grounding planes other places, they’re going to want to do the same thing.”

In the meantime, Tajer said pilots will now get more 737 Max 8 training.

“We’ve talked to American Airlines about the additional training. As a matter of fact American just informed us that they have simulators coming to delivery for us, so that we can train in the actual simulators,” Tajer said.

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A Boeing spokesperson said teams are headed to Ethiopia along with other U.S. investigators to help determine a cause.