A Seattle-bound Southwest Airlines flight returned to Denver International Airport shortly after takeoff on Friday evening, an airport spokesman confirmed.
The pilot decided to fly back to the airport about 20 minutes after takeoff when the smell of smoke was detected in the cabin, Heath Montgomery, spokesperson for Denver International Airport, told NBC News.
The airline referred to it as "an electrical smell in the cabin" of Flight 541.
"The captain declared an emergency, and the plane landed uneventfully in Denver," Melissa Ford, a spokeswoman for Southwest Airlines, told NBC News.
Firefighters responded to the scene after the plane landed and were unable to find any signs of smoke or fire, Montgomery said.
"The pilots were joking around about an early landing and a few minutes later they said we were making an emergency return to Denver because of the smell of smoke in the cabin,” passenger Victor Fitzjarrald told NBC News.
“We could smell a little bit - most of us describe it as burnt coffee,” Fitzjarrald, 30, said. “The stressful part is still being on the ground four hours late…and no mention of any compensation. We have folks that are pretty upset.”
The crew was "professional and did a great job," he noted.
Fitzjarrald said passengers were notified that a new plane and crew had been found and they were scheduled to make their way toward their original destination at 10 p.m. local time (midnight ET).
The aircraft has been taken out of service for further review, according to Ford, who said the flight's 143 passengers were put on a different aircraft that is expected to arrive in Seattle about four hours past the originally scheduled arrival time.