The Lufthansa plane sat on the tarmac at Denver International Airport for three hours Sunday night due to unspecified technical problems, 9News reported.
As mechanics labored to fix the broken AC, passengers huddled into the coolest section of the plane.
"They said there were some technical and mechanical malfunctions," Sarah Bogue, told 9News by phone as she and her toddler waited aboard the plane. "They ran out of water. I can't even tell you how hot it is in here. They should at least let us off the plane to wait."
Paramedics were called 90 minutes into the delay, but no one needed treatment.
After three hours, around 8:30 p.m., passengers were finally allowed off the plane. They were re-boarded about an hour later and took off for Frankfurt just after 10 p.m.
The U.S. Department of Transportation allows domestic carriers to keep passengers on the tarmac for up to three hours, but international airlines can set their own rules. Lufthansa sets a four-hour limit for on-the-ground delays.