President Donald Trump tweeted advice to Boeing on Monday about its 737 Max aircraft following two deadly crashes that has prompted airlines to ground the plane: "I would FIX the Boeing 737 MAX, add some additional great features, & REBRAND the plane with a new name."

Mr. Trump added, "No product has suffered like this one. But again, what the hell do I know?"

Mr. Trump, who owned the Trump Shuttle airline from 1989 to 1992, has previously aired his views on the airline industry and Boeing's woes via Twitter. Last month, he bemoaned the complexity of modern airplane technology after the second deadly crash of a Boeing 737 Max 8, which occurred five months after another plane of the same make crashed and left no survivors.

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"Airplanes are becoming far too complex to fly," the president tweeted in March. "Pilots are no longer needed, but rather computer scientists from MIT. I see it all the time in many products."

In the case of Monday's tweet, Mr. Trump tried to downplay his marketing knowledge, writing, "What do I know about branding, maybe nothing (but I did become President!)"

On Sunday, American Airlines said it will continue canceling all flights with Boeing 737 Max planes through Aug. 19. The airline said about 115 flights per day would be canceled. American had previously said it would suspend flights of 737 Max aircraft through June 5.