Holidaymakers are accusing airlines and travel firms of hiking prices following the demise of Thomas Cook.
David Kirkwood posted screenshots on social media appearing to show how a Jet2.com holiday in Cyprus increased in cost by £800 between 7.30am and 11.30am on Monday.
He described the firm as "soulless", "money grabbing" and "opportunist".
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Another disappointed customer with the Twitter username @westmitc said he planned to book a holiday with the firm last night but waited until today as he had a question to ask, by which time the cost had increased by £248.
"They're taking the p*** because of Thomas Cook," he added.
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A woman using the Twitter handle @cherrie2502 stated that she booked a Thomas Cook flight for £215 last week when a Jet2.com flight on the same route was £284, but the latter has now gone up to £511.
"Way to go on price gouging," she added.
A spokeswoman for Jet2.com said: "Our pricing, as is common practice in the travel industry, is based on the principle of supply and demand.
"As supply reduces, an inevitable consequence is that prices increase. However, we are looking at adding more supply (flights and seats) to help customers at this time."
Twitter user @azza78 said Virgin Atlantic flights to Florida have gone up by £400 since the announcement by Thomas Cook.
She told the airline: "Would be a lovely gesture if you price matched!"
A Thomas Cook customer booking replacement flights with Virgin Atlantic accused the airline of "making extra profit from people's misery" after the price increased by £150 as he was completing the transaction.