The Department of Transportation on Wednesday announced a rule that will require airlines to make lavatories on new single-aisle planes large enough for two people to enter in a move to make bathrooms more accessible.

"Traveling can be stressful enough without worrying about being able to access a restroom; yet today, millions of wheelchair users are forced to choose between dehydrating themselves before boarding a plane or avoiding air travel altogether," said Transportation Secretary Pete Buttigieg in a press release announcing the rule.

The rule was authorized through the Air Carrier Access Act, and it specifies that the lavatories will need to be large enough passengers with disabilities and their attendants to enter and maneuver within the space.

In twin-aisle aircraft, accessible lavatories have been required since 1990. Yet as the range and fuel efficiency of single-aisle aircraft have increased, these planes now take longer flights. That can leave passengers with disabilities with no way to use the bathroom for hours on end.

John Morris, the founder of WheelchairTravel.org, is a triple amputee who travels frequently. Next week, he's flying from Boston to Los Angeles on a plane without an accessible lavatory.

"Denying someone the ability to go to the bathroom is certainly a form of torture that has been used by rogue individuals in human history," Morris said. "I just don't think that that should be the case on an airplane."

Commercial aircraft have a lifespan of decades. That means that years into the future, without retrofitting the aircraft, disabled travelers will still encounter inaccessible lavatories -- a problem Morris himself has encountered. He recounted a trip he took in 2016 from Seattle to Tokyo on a wide-body airplane. Halfway over the Pacific, Morris, who said that airlines are opaque about sharing accessibility information before passengers book flights, discovered the aircraft he was on had been delivered before the accessible lavatory rule went into effect in 1990. There was no bathroom he could use.

"We need to ensure that people have the ability to go to the bathroom when they need to, without significant barriers being in place between them and carrying out that bodily function that is something that every human being needs to do," said Morris.

Passengers won't see these changes anytime soon, since the requirement increasing the lavatory size applies to aircraft ordered 10 years after the rule goes into effect.

"We've got to wait and that's not great -- but I'm going to balance this a little bit and say 10 years is not a long time in aviation," said Chris Wood, the founder of the advocacy organization Flying Disabled. "In my heart, I wanted at least maybe three or five years for this to start to happen."

ABC News' Sam Sweeney contributed to this report.