SkyWest Passengers Who Fainted Sat in the Middle of the Plane

— -- Why three people lost consciousness on a SkyWest Airlines flight this week remains a mystery, but they shared at least one thing: proximity.

The passengers who fainted were in two rows in the middle of the plane -- rows 11 and 12 -- over the wings on their flight from Chicago to Hartford, Connecticut, Wednesday.

But at least one expert doubts that’s relevant.

"The cabin is pressurized exactly the same from the front to the back," ABC News aviation analyst John Nance said today. "The fact that they're located [closely] simply means one person was noticed to be lethargic. ... We don't know what the rest of the cabin was like."

SkyWest Airlines Flight 5622 -- operating as United Express on behalf of United Airlines -- had nearly 80 passengers on board when the first person fainted.

A passenger and nurse on board, Mary Cunningham, attended to two passed out passengers and saw a flight attended also get lightheaded.

"And at that point I was thinking, who else was going to be affected? Who's next?" Cunningham said. "I myself started to feel lightheaded, dizzy, just I thought I was going to pass out."

The power of suggestion can be "very psychologically powerful on an airplane," Nance, a former commercial and Air Force pilot, said, "where people are on-edge to begin with."

"At the altitude they're at, any exertion is going to make you woozy," Nance said. "I'm sure that entire airplane was woozy, they just didn't recognize it."

While the Federal Aviation Administration says the pilot likely feared a potential cabin pressure problem and dropped the plane to get breathable air, SkyWest said there were no indications of a pressurization problem on the plane.

After the plane landed, the three people who lost consciousness, as well as 17 others, were evaluated, the Associated Press reported. No one was hospitalized, the airline said in a news release.

Eric Weiss, spokesman for the National Transportation Safety Board, said, "We're trying to understand the circumstances before we decide on what, if any action, we would take," according to the AP.

ABC News' David Kerley and the Associated Press contributed to this story.