SEATTLE, WA - JUNE 27: Boeing 737 MAX airplanes are stored on employee parking lots near Boeing Field, on June 27, 2019 in Seattle, Washington. After a pair of crashes, the 737 MAX has been grounded by the FAA and other aviation agencies since March, 13, 2019. The FAA has reportedly found a new potential flaw in the Boeing 737 Max software update that was designed to improve safety. (Photo by Stephen Brashear/Getty Images)
PHOTO: Stephen Brashear/Getty Images North America/Getty Images
SEATTLE, WA - JUNE 27: Boeing 737 MAX airplanes are stored on employee parking lots near Boeing Field, on June 27, 2019 in Seattle, Washington. After a pair of crashes, the 737 MAX has been grounded by the FAA and other aviation agencies since March, 13, 2019. The FAA has reportedly found a new potential flaw in the Boeing 737 Max software update that was designed to improve safety. (Photo by Stephen Brashear/Getty Images)
Now playing
01:06
Boeing to take nearly $5 billion charge for 737 Max woes
Now playing
03:43
Boeing never tested the failure of critical sensor
A Boeing 777X model is displayed at the Airshow China 2018 in Zhuhai in southern China's Guangdong province on November 7, 2018. (Photo by WANG Zhao / AFP)        (Photo credit should read WANG ZHAO/AFP/Getty Images)
PHOTO: WANG ZHAO/AFP/Getty Images
A Boeing 777X model is displayed at the Airshow China 2018 in Zhuhai in southern China's Guangdong province on November 7, 2018. (Photo by WANG Zhao / AFP) (Photo credit should read WANG ZHAO/AFP/Getty Images)
Now playing
02:24
Boeing's reputation on the line after 737 Max 8 crashes
VICTORVILLE, CA - MARCH 27:  A number of Southwest Airlines Boeing 737 MAX aircraft are parked at Southern California Logistics Airport on March 27, 2019 in Victorville, California. Southwest Airlines is waiting out a global grounding of MAX 8 and MAX 9 aircraft at the airport.  (Photo by Mario Tama/Getty Images)
PHOTO: Mario Tama/Getty Images
VICTORVILLE, CA - MARCH 27: A number of Southwest Airlines Boeing 737 MAX aircraft are parked at Southern California Logistics Airport on March 27, 2019 in Victorville, California. Southwest Airlines is waiting out a global grounding of MAX 8 and MAX 9 aircraft at the airport. (Photo by Mario Tama/Getty Images)
Now playing
02:33
More bad news for Boeing
RENTON, WA - MARCH 11: The Boeing 737-8 is pictured on a mural on the side of the Boeing Renton Factory on March 11, 2019 in Renton, Washington. Two of the aerospace company's newest model airliners have crashed in less than six months. (Photo by Stephen Brashear/Getty Images)
PHOTO: Stephen Brashear/Getty Images North America/Getty Images
RENTON, WA - MARCH 11: The Boeing 737-8 is pictured on a mural on the side of the Boeing Renton Factory on March 11, 2019 in Renton, Washington. Two of the aerospace company's newest model airliners have crashed in less than six months. (Photo by Stephen Brashear/Getty Images)
Now playing
02:59
Source: Pilots trained on Boeing 737 Max in 2.5-hour course
People stand near collected debris at the crash site of Ethiopia Airlines near Bishoftu, a town some 60 kilometres southeast of Addis Ababa, Ethiopia, on March 11, 2019. - An Ethiopian Airlines Boeing 737 crashed on March 10 morning en route from Addis Ababa to Nairobi with 149 passengers and eight crew believed to be on board, Ethiopian Airlines said. (Photo by Michael TEWELDE / AFP)        (Photo credit should read MICHAEL TEWELDE/AFP/Getty Images)
PHOTO: MICHAEL TEWELDE/AFP/Getty Images
People stand near collected debris at the crash site of Ethiopia Airlines near Bishoftu, a town some 60 kilometres southeast of Addis Ababa, Ethiopia, on March 11, 2019. - An Ethiopian Airlines Boeing 737 crashed on March 10 morning en route from Addis Ababa to Nairobi with 149 passengers and eight crew believed to be on board, Ethiopian Airlines said. (Photo by Michael TEWELDE / AFP) (Photo credit should read MICHAEL TEWELDE/AFP/Getty Images)
Now playing
02:38
CNN reporter: Crash report a blow for Boeing
People walk past a part of the wreckage at the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia March 10, 2019. REUTERS/Tiksa Negeri
PHOTO: TIKSA NEGERI/REUTERS
People walk past a part of the wreckage at the scene of the Ethiopian Airlines Flight ET 302 plane crash, near the town of Bishoftu, southeast of Addis Ababa, Ethiopia March 10, 2019. REUTERS/Tiksa Negeri
Now playing
02:55
Everything we know about the Ethiopian plane crash
Boeing 737 Max simulator flight
PHOTO: CNN
Boeing 737 Max simulator flight
Now playing
02:45
Inside the training simulator for Boeing 737 Max 8 plane
Now playing
01:39
Trump: Boeing 737 Max 8 and 9 aircraft grounded
RENTON, WA - MARCH 14: Boeing 737 MAX airplanes, including the 737 MAX 9 test plane (L), are seen at Renton Municipal Airport, on March 14, 2019 in Renton, Washington. The 737 MAX, Boeing's newest model, has been been grounded by aviation authorities throughout the world after the crash of an Ethiopian Airlines 737 MAX 8 on March 10.  (Photo by Stephen Brashear/Getty Images)
PHOTO: Stephen Brashear/Getty Images North America/Getty Images
RENTON, WA - MARCH 14: Boeing 737 MAX airplanes, including the 737 MAX 9 test plane (L), are seen at Renton Municipal Airport, on March 14, 2019 in Renton, Washington. The 737 MAX, Boeing's newest model, has been been grounded by aviation authorities throughout the world after the crash of an Ethiopian Airlines 737 MAX 8 on March 10. (Photo by Stephen Brashear/Getty Images)
Now playing
01:55
Report: Pilots raced for manuals as plane went down
A grounded Lion Air Boeing Co. 737 Max 8 aircraft sits on the tarmac at terminal 1 of Soekarno-Hatta International Airport in Cenkareng, Indonesia, on Tuesday, March 15, 2019. Sundays loss of an Ethiopian Airlines Boeing 737, in which 157 people died, bore similarities to the Oct. 29 crash of another Boeing 737 Max plane, operated by Indonesias Lion Air, stoking concern that a feature meant to make the upgraded Max safer than earlier planes has actually made it harder to fly. Photographer: Dimas Ardian/Bloomberg via Getty Images
PHOTO: Dimas Ardian/Getty Images
A grounded Lion Air Boeing Co. 737 Max 8 aircraft sits on the tarmac at terminal 1 of Soekarno-Hatta International Airport in Cenkareng, Indonesia, on Tuesday, March 15, 2019. Sundays loss of an Ethiopian Airlines Boeing 737, in which 157 people died, bore similarities to the Oct. 29 crash of another Boeing 737 Max plane, operated by Indonesias Lion Air, stoking concern that a feature meant to make the upgraded Max safer than earlier planes has actually made it harder to fly. Photographer: Dimas Ardian/Bloomberg via Getty Images
Now playing
01:54
Report: Off-duty pilot saved Lion Air flight day before crash
Rescuers work at the scene of an Ethiopian Airlines flight crash near Bishoftu, or Debre Zeit, south of Addis Ababa,  Ethiopia, Monday, March 11, 2019. A spokesman says Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution, following the crash of one of its planes in which 157 people were killed. (AP Photo/Mulugeta Ayene)
PHOTO: Mulugeta Ayene/AP
Rescuers work at the scene of an Ethiopian Airlines flight crash near Bishoftu, or Debre Zeit, south of Addis Ababa, Ethiopia, Monday, March 11, 2019. A spokesman says Ethiopian Airlines has grounded all its Boeing 737 Max 8 aircraft as a safety precaution, following the crash of one of its planes in which 157 people were killed. (AP Photo/Mulugeta Ayene)
Now playing
01:51
Authorities: Similarities between Ethiopian, Lion Air crashes
PHOTO: CNN Indonesia
Now playing
02:58
Lion Air flight dove over 24 times before crash
(CNN Business) —  

United Airlines passengers fearful of boarding a Boeing 737 Max will be able to rebook flights for free once United starts flying the planes again.

“If you get to the gate and it’s not an airplane you want to fly on for whatever reason, if it’s a Max, we’ll put you on another flight,” said Andrew Nocella, the airline’s chief commercial officer, at an investor conference Wednesday.

Nocella said it’s probably too soon to tell what passenger reaction will be once the 737 Max returns to service. The Boeing jet has been grounded since March, following two fatal crashes that killed 346 people.

“We need to get through the recertification process, return the aircraft to service and see how things go,” he said. “If somebody is uncomfortable getting on the aircraft… we want to make sure we can put them on a different aircraft.”

A United spokesman confirmed the rebooking would be done without the passengers being required to pay any change fee.

Nocella said that United’s website will notify passengers booking a flight what equipment it expects to use. Those plans sometimes change at the last moment, but postings at the gate will provide passengers with the most current information about what aircraft will be used on their flights.

American Airlines (AAL), which also has the grounded jets in its fleet, said it has yet to set a policy for dealing with customers who don’t want to fly the 737 Max.

“Once the aircraft is cleared to fly again, American will continue to look at ways to reiterate to our customers that our pilots are the best in the business and would never fly an unsafe aircraft,” said a company spokesperson. “We will always work to ensure we have policies and procedures in place that take care of our customers. Once these policies are rolled out, [we] will assist our customers if they are still concerned flying on the Max.”

Southwest (LUV), the third US airline with the planes already in its fleet, has the most flexible rules among airlines for allowing passengers to change flights without change fees. A spokesperson said that if a passenger does not want to fly the 737 Max, “we will offer them full flexibility.”

Delta (DAL)’s fleet has no 737 Max planes.

It’s unclear when the 737 Max will return to the skies. Boeing (BA) hopes to have the plane cleared to fly again by early next month. Southwest CFO Tammy Romo said at the same investor conference Wednesday that the company expects to get approval to fly the planes in mid November. But the airlines don’t plan to add flights they have canceled because of the grounding until the end of this year, at the earliest.