U.S. Transportation Secretary Pete Buttigieg said the Federal Aviation Administration will rigorously assess Boeing after the blowout of a fuselage section on an Alaska Airlines flight in January.

To maintain airline safety, “that means an enormous amount of rigor in dealing with Boeing, in dealing with any regulatory issue,” Buttigieg said on Fox News Sunday. “And that’s exactly what the FAA is doing.”

Boeing has faced scrutiny from lawmakers, regulators and increasingly passengers after a series of high-profile flight incidents this year, most notably the blowout of a fuselage section on a brand-new 737 MAX 9 during an Alaska Airlines flight in January.

Shares of Boeing fell 1.6% in premarket U.S. trading on Monday, after reports over the weekend that the Justice Department opened a criminal investigation into the Alaska Air incident. The head of Delta Air Lines Inc. told Bloomberg separately that he expects further delays to the yet-to-be certified 737 MAX 10.