Frontier eventually admitted there had been a mistake By 10pm Eastern Time, although travellers complained
The airline apologised for the "technical problem" which had caused the email to go out to customers. Frontier urged passengers to check their flight details on their website to confirm their travel status.
A spokesperson for the airline told USA Today that the source of the email was under investigation.
However this will be small comfort to the travellers who had already made backup travel arrangements.
"I was terrified because these (flights) are coming up in a few days," Steven Harms told USA Today, as considered rebooking his family's travel last minute.
"If we had to rebook it would be a really tough situation just because it's the holiday."
A report by Smartertravel.com found that air fares over the Sunday before Thanksgiving were up to 70 per cent above average, even more when booked last minute.