Some Thanksgiving travelers received an alarming email on Thursday from low-cost carrier Frontier Airlines warning them that their flight had been changed or canceled. It was a mistake. 

Late Thursday, Frontier said the email was sent "in error" and apologized. Consumers complained about the confusing email on Twitter, with some saying they couldn't get through to Frontier's customer service.

"I received an email saying flight was changed to call 801-401-9005, I can't through just busy signal," one traveler wrote on Twitter. "When I look in the frontier app flight has not changed? Can someone help me."

Frontier on Friday advised passengers tp check their trips by entering their confirmation numbers on its website. 

Thanksgiving is among the busiest travel periods of the year. Next week, about 4.5 million Americans will fly to visit family and friends, up almost 5% from a year ago, according to AAA. 

Consumers weren't impressed with Frontier's handling of the glitch. Others noted that it took hours for Frontier to respond to questions about the wayward email. 

Frontier is among the lowest-rated airlines by Consumer Reports, which based its analysis on 55,000 responses from its subscribers.