A man says crew members on a SkyWest Airlines flight refused to allow his brother with autism to sit near a family member Friday and walked off the plane, forcing all 75 passengers to deplane and board another flight three hours later.

Now, the crew, including the pilots, have been grounded while the airline investigates the incident.

Ayomide Isola, 23, was on SkyWest Flight 3596 from Detroit to Houston with his mother, sister and 21-year-old brother, Tayo, who is nonverbal and unable to express himself. SkyWest is a connection carrier for Delta and other major airlines.

Isola, a graduate student at the University of Houston, said in a now-viral Facebook post that he and his family arrived at the gate to learn they were all seated apart. They were among the last people to board the flight because a U.S. Customs and Border Protection computer outage caused hours-long delays at airports Friday, he said.

Once they boarded the plane, a woman quickly volunteered to switch seats with Tayo so he could be near his sister during the more than two-hour flight.

Ayo Isola, right, with his brother, Tayo. Courtesy Ayo Isola

"My brother has to sit with one of our family members he is comfortable with," Isola told NBC News on Monday.

A flight attendant became outraged and approached Tayo to tell him he needed to return to his assigned seat, Isola said. But his brother could not oblige because he does not respond to verbal cues.

Isola said he and his family explained to the flight attendant that Tayo is special needs and "that this small accommodation would be necessary." But she would not relent, he said, and instead, brought in a gate supervisor who sided with the family.

"The supervisor was like, 'That happens all the time,'" Isola said. "She was confused as to why the flight attendant was making such a big deal about it."

Other passengers on the flight were defending the family and telling the flight attendant she was being discriminatory, Isola said.

After already being delayed for nearly an hour, the flight attendant then consulted the pilot and advocated for the family and the passenger who switched seats with Tayo to be booted from the flight. She told the pilot they were a "safety hazard," Isola said.

After a discussion with the pilot and flight attendant, Isola said the pilot instructed everyone on the plane to exit the aircraft.

Airport security meanwhile told the pilot there was no safety issue and that the flight should resume, according to Isola.

The pilot and his crew refused and exited the terminal, Isola said. He and the 74 other passengers had to exit the aircraft and wait three hours for a new crew to board the plane.

"When the new crew came in, everything went smoothly," Isola said.

Isola said he shared his experience to highlight the "ignorant, bigotry and blatant discrimination that unfortunately exists in people today."

"It is not right to treat people with special needs as if they are unworthy of your time or effort," he said. "They are people first, defined by all of their abilities and not condemned by their disabilities."

Delta said in a statement Monday that it was reviewing the details of the incident to "better understand what happened."

“Delta apologizes to customers on flight 3596, operated by Delta Connection partner SkyWest, for any inconvenience following an onboard event," a spokeswoman told NBC News.

SkyWest acknowledged the flight experienced a delay in boarding "as a result of an issue regarding customer seat assignments," and said it was investigating the incident. According to a spokeswoman, the crew was initially unaware of the traveler’s disability.

"We are committed to providing exceptional onboard service to all of our customers and are working with our partner Delta to reach out to the customers," the spokeswoman said.

Isola said he doesn't believe the crew should be allowed to fly any longer. If they are, the airline should require they undergo sensitivity training, he said.

"There’s a certain sensitivity level, compassion level you need to have to fly with travelers who have disabilities," Isola said. "And if you can’t do that, then you shouldn’t be in this business."