Thomas Cook's clients have told the EXE News that flight prices have tripled in some cases.
According to analysts, prices reflect high demand for flights with few available seats.
"When sales on popular routes grow rapidly, prices will go up," said John Strickland, an analyst at JLS Consulting, who said September is a popular holiday month outside the school holidays and many flights were already full.
Strickland said the airlines could have stopped the price increase, but the companies have to do business.
“Thomas Cook was destroyed because he had huge debts and was at a loss. This is a fragile business. Over a dozen airlines have gone down, ”said Strickland. "If airlines don't make the profits they can on minority flights, they have no chance to survive."
However, according to Mills, rising prices are particularly bad news for travelers who are already in a state of shock.
Kevin Spence was due to fly to Florida with his family in June next year. The trip was planned for two years and money was set aside for it.
After looking at airfares before Thomas Cook's bankruptcy on Sunday and the following morning, it was found that they had risen sharply.
Previously, the flight cost £ 1,800 to a family of four and now £ 2,500, Spence said.
"I'm stunned," Spence said. “The price of a holiday trip is now rising beyond our budget. I am now in a situation where I may have to stop it altogether. ”