The 737 MAX has been given the all-clear to begin its return to commercial service, but those fearful of booking a flight on the aircraft shouldn't worry.

Airlines that fly the planes will not force passengers to keep their flights if they don't feel comfortable following the Federal Aviation Adminstration's order that allows the Boeing 737 MAX's return. Free ticket changes will be offered to passengers that have booked a flight on the aircraft as a way to reassure customers, NBC News reported.

In an open letter to passengers, David Seymour, chief operating officer at American Airlines, said, “We know that restoring our customers’ confidence in this aircraft will come with time and importantly, transparency and flexibility.

“If a customer doesn’t want to fly on the 737 MAX, they won’t have to. Our customers will be able to easily identify whether they are traveling on one even if schedules change. If a customer prefers to not fly on this aircraft, we’ll provide flexibility to ensure they can be easily re-accommodated.”

The 737 MAX was grounded for 20 months after 346 people were killed aboard Lion Air Flight 610 in 2018 and Ethiopian Airlines Flight 302 in 2019.

The FDA has returned the 737 MAX to service but with restrictions for the airlines that use them, including a revised pilot training program, new airworthiness certification for the airlines, and additional maintenance steps for grounded aircraft.

But passengers that are uncomfortable boarding the 737 on their next flight do have options.

Brian Kelly, founder and CEO of The Points Guy, a travel advice site, told NBC News, “For now, most airlines that have the plane will show it as the Boeing 737 Max 8 or Max 9 at booking.”

This will allow passengers to select the aircraft they want to fly on when traveling. But this could change, according to Kelly, who said, “There's been talk that some airlines could rebrand the Max as a 737-8 or Boeing 737-9 — which is different from the non-Max Boeing 737-800 or 737-900. That's something to look for.”

Seymour said that American Airlines is taking a “phased approach to return the aircraft to service.”

“We will begin with non-commercial flights in early December before the official return to service date to demonstrate that the 737 MAX is as safe as every plane we fly at American,” he said.

Starting on Dec. 29 through Jan. 4, 2021, American will have two flights a day with 737 MAX, one round trip from its hub in Miami to LaGuardia in New York. The company said it then expects to gradually phase in more 737 MAX aircraft throughout January 2021, adding up to 36 departures from Miami, depending on the day of the week.

American Airlines plane An American Airlines plane is pictured. Photo: GETTY IMAGES NORTH AMERICA / JOE RAEDLE