"I thought we were done," he said Thursday, one day later. "There was no doubt in my mind that we weren't going to land."
Johnson was flying with his brother, his girlfriend and his 8-month-old son when he says a flight attendant came over the speaker asking for someone who was medically trained to help with a sick passenger.
Minutes later, Johnson says, the attendant announced there was a pressurization problem and told passengers to prepare for the emergency landing.
"You're going to feel dizzy and woozy and lightheaded, and you're not going to be able to breathe," Johnson recalled the flight attendant saying.
The Federal Aviation Administration on Wednesday initially reported a pressurization problem with SkyWest Flight 5622, and said it would investigate. It later issued a statement that did not reference any pressurization issues.
"It was like being trapped and you couldn't do anything. You have no control over it. Your body just felt pressured," Johnson said.
Johnson said his girlfriend was seeing spots and that "when I was blinking, it was really bright. I could barely see."
According to Marissa Snow, spokeswoman for SkyWest, three passengers reported a loss of consciousness while on the flight.
Fifteen passengers were examined by medical personnel at the Buffalo airport, but no one was transported to the hospital, she said.
The spokeswoman said that maintenance personnel found no indication of a pressurization problem with the aircraft, an Embraer E170, and that the airline continues to investigate the cause.
An official with the National Transportation Safety Board told CNN that the agency is in communication with the FAA and SkyWest to gather information on the incident to better understand what took place.
Mary Cunningham was the nurse on board who attended to the first sick passenger.
"There was a woman, very lethargic, very nauseous, turning gray, just not looking good," Cunningham said.
After administering oxygen to the woman, Cunningham, a nurse at Yale-New Haven Hospital in Connecticut, returned to her seat.
Soon after, Cunningham said, she was called up again by the flight attendant after another women near the first started to lose consciousness.
"It was something that was affecting oxygen in that area," which was near the middle of the plane, she said.
Cunningham said she had to return to her seat after feeling lightheaded.
There were 84 passengers on board the plane, including nine crew members.
Flight 5622 was originally scheduled to fly from Chicago to Hartford, Connecticut. The plane descended 28,000 feet in three minutes.
"It would feel like a roller coaster -- when you're coming over the top and you're going down," CNN aviation analyst Mary Schiavo said, describing how such a descent would feel. "You know that these pilots knew they were in a very grave and very serious situation."
Johnson, flying to visit his parents with their only grandchild, was glad that roller coaster ride ended safely.
"It was a shaky ride. It wasn't anything I would like to experience again," he said.