New York 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.