A plane carrying Ann Romney was descending rapidly in hopes of making an emergency landing in Denver.

“The cabin filled pretty rapidly with smoke,” said Susan Duprey of Concord, who travels with Romney as a senior adviser.

As the smoke spread through the plane Friday, Duprey said, she was focused on the wife of GOP presidential nominee Mitt Romney. Both were fighting burning sensations in their eyes and throats from either the smoke or a fire suppressant.

“One thing that went through my mind was oxygen for Mrs. Romney,” Duprey recalled in a phone interview from California on Saturday. She knew the Secret Service carried oxygen and assumed the plane did, as well.

“I inquired about that,” she said. “We agreed at that point we didn’t need oxygen.”

Those charged with protecting Mrs. Romney gauged the situation’s seriousness.

“The Secret Service was quickly calculating what needed to get done when it appeared the flight attendant couldn’t control the smoke,” Duprey said. “They rapidly moved to the front of the plane to talk to the pilot and immediately made the decision to land the plane.”

She said she never saw flames on the plane, which left Omaha, Neb., destined for California with 10 aboard, including the crew.

“Before we landed, the Secret Service made a determination on who should emerge from the plane in what order, and obviously Mrs. Romney was Number 1,” Duprey said. About 10 fire trucks arrived, and firefighters entered the empty plane after it landed in Denver.

The emergency landing was due to “apparently an electrical fire” aboard the plane, Romney for President Press Secretary Andrea Saul said on Twitter. “All okay. Thank goodness.”

Duprey said Mrs. Romney talked to her husband within a few minutes of arriving at an airport building. “Gov. Romney was on the phone, and he knew before we were able to make any calls,” Duprey said.

“I think Mrs. Romney did a wonderful job of taking this in stride and paying attention to what had to be done — not to panic, to get off the plane quickly and get away from the plane, and she executed all of those steps without any sign of panic,” she said.

Duprey and Mrs. Romney boarded a different plane later Friday to make it to California.

“I think we were OK about getting on another plane,” she said.