Boeing's 737 MAX to fly in US with paying passengers for 1st time in nearly 2 years

Boeing's 737 MAX is set to take off Tuesday morning with paying passengers for the first time in almost two years, after two fatal crashes forced U.S. regulators to ground the plane in March 2019.

American Airlines Flight 718 plans to leave Miami at about 10:30 a.m. and arrive at Laguardia Airport in New York at 1:30 p.m.

The MAX crashes in Ethiopia and Indonesia were tied to an automated flight control system that misfired in both crashes, leaving pilots struggling to regain control and altitude of the plane. Boeing has since rewritten the MAX flight computer software, receiving the Federal Aviation Administration's approval for the jet to reenter commercial service on Nov. 18.

American flew journalists on a demo flight from Dallas to Tulsa, Oklahoma, in early December in an effort to reassure passengers that the upgraded MAX is safe.

American is the only U.S. carrier that announced plans for the jet to reenter service in 2020. United Airlines said it will start flying the MAX out of its Denver and Houston hubs on Feb. 11. Southwest Airlines estimated that the MAX will return to service no sooner than March.

American, Southwest and United have all said they will be completely transparent with customers who are scheduled to fly on a MAX and will allow them to rebook with no change fee or request a refund if they do not feel comfortable.

Several people who lost loved ones in the crashes have said that they don't believe the MAX should return to the skies.

"The truth is that 346 people are now dead because Boeing cut corners, lied to regulators and simply considers this the cost of doing business," Yalena Lopez-Lewis, whose husband Antoine Lewis died in the Ethiopian Airlines Flight 302 crash, said in a statement on Monday. "Boeing proclaims to be a changed company since the crashes, but in court they continue to hide documents, deny that they put profits over safety and refuse to be held accountable. It is infuriating that American Airlines is in effect rewarding Boeing for the corrupt and catastrophic process that led to the MAX."

Lopez-Lewis along with six other family members of Ethiopian Airlines Flight 302 sent a letter to Department of Transportation Secretary Elaine Chao and FAA Administrator Steve Dickson last week requesting that they rescind the airworthiness directive that ungrounded the Boeing 737 MAX.

In response to the letter, the FAA told ABC News, "Working closely with other international regulators, the FAA conducted a thorough and deliberate review of the 737 MAX. We are confident that the safety issues that played a role in the tragic accidents involving Lion Air Flight 610 and Ethiopian Airlines Flight 302 have been addressed through the design changes required and independently approved by the FAA and its partners."

The Senate Commerce Committee released its investigation report on the MAX on Dec. 18. It followed a similar scathing report released by House investigators in September that concluded technical design flaws, faulty assumptions about pilot responses and management failures by both Boeing and the FAA led to the collisions.

"Our findings are troubling," U.S. Sen. Roger Wicker, R-Miss., chairman of the Senate Committee on Commerce, Science, and Transportation said in a statement. "The report details a number of significant examples of lapses in aviation safety oversight and failed leadership in the FAA. It is clear that the agency requires consistent oversight to ensure their work to protect the flying public is executed fully and correctly."

Last week, Congress passed bipartisan legislation meant to strengthen the oversight of the certification process.

ABC News' Sam Sweeney contributed to this report.