england-and-wales
On the basis of the circumstances described, the trader's behaviour seems tantamount to more than one offence.
The behaviour known as 'bait advertising' is described at paragraph 5 of Schedule 1, Consumer Protection from Unfair Trading Regulations 2008 (CPRs):
- Making an invitation to purchase products at a specified price without disclosing the existence of any reasonable grounds the trader may have for believing that he will not be able to offer for supply, or to procure another trader to supply, those products or equivalent products at that price for a period that is, and in quantities that are, reasonable having regard to the product, the scale of advertising of the product and the price offered (bait advertising).
Regulation 12 CPRs makes an offence of such behavior:
- A trader is guilty of an offence if he engages in a commercial practice set out in any of paragraphs 1 to 10, 12 to 27 and 29 to 31 of Schedule 1.
Advertising a price promotion for a product that is not in fact available at the advertised price is a 'misleading action' at Regulation 5(4)(g) and (h) CPRs. Regulation 9 CPRs makes offences of 'misleading actions'.
Other regulations may be relevant, such as misleading omissions at Regulation 6 CPRs. This is an offence too - at Regulation 10 CPRs. This is the omission, hiding or misleading provision of 'material information', i.e. "the information which the average consumer needs, according to the context, to take an informed transactional decision". In other words, information that would tend to affect the decision of the average consumer. Such as, "we might take your money without supplying you the product."
(Quibbles in comments about whether the money was in fact taken by the trader or blocked by the bank seem besides the point. The trader misled the consumer with the effect that the consumer cannot use this particular money for the time being and hasn't been given the product either.)
I'm sure in this case there was no criminal intent and that it's down to technology, race conditions or glitches, but the consequences are the same. The law doesn't have the effect of "it's OK if it's a glitchy real-time flight price comparison system," it has the effect of, "if there is a risk you can't supply a thing at the price you said you would supply it for, you have to make that risk clear to the customer - especially before you take their money."
Writing more generally and in reaction to some other answers and comments here:
It's not sufficient to point to terms and conditions and say the consumer should have read them.
Consumers have rights under contract law and the Consumer Rights Act 2015. Traders must not behave in ways that are considered 'banned practices', 'misleading practices', 'aggressive practices' or otherwise 'unfair commercial practices' under the Consumer Protection from Unfair Trading Regulations 2008 (CPRs). The trader must abide by The Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013.
The law requires fair and open dealing with consumers, transparency, timeliness, and particular prominence for terms that are unfavourable to consumers.
Terms must be fair. Information likely to make a difference to the consumer's decision should be prominent and close to the headline, price or call to action (e.g. a 'buy now' button). There shouldn't be a burden on the consumer to take extra steps such as scrolling down or clicking a link to another page.
When prices are subject to frequent changes, the trader should monitor the position and, when necessary, act promptly to withdraw the offer. The trader should not take the consumer's money and then withdraw the offer from that consumer!
Consumers tend to think they have entered into a binding contract once they have confirmed they want to buy and the system has accepted their payment details. Generally, if the trader is then unable to fulfil the contract, the consumer may reasonably believe the trader is in breach of contract. If the consumer's money has been taken or is otherwise made unavailable to the consumer, the consumer might be entitled to compensation.
The Competition & Markets Authority (CMA) has expressed the view that terms and conditions along the lines of "the contract is only formed when the goods are dispatched" risk failing the fairness test under section 62, Part 2, Consumer Rights Act 2015. This is because such a term or notice is likely to cause a significant imbalance in the parties' rights and obligations under the contract to the detriment of the consumer, contrary to the requirement of good faith (section 62(4)). It is insufficient to have such a term behind a link and/or buried in a wall of terms.
(If a term said something like, "In the event we can't supply at this price then we will refund you and give you £100 cash" or "... we'll offer a better alternative for no extra charge" then there would be a benefit to the consumer, therefore the term would be fair / less unfair to the consumer, therefore less likely to be unlawful.)
Finally, some if not all of the big online aggregators have done some unfair things in their time! Indeed, some so-called 'disruptors' have 'disrupted' by simply ignoring/breaking the law.
The CMA has investigated hotel booking websites, car rental brokers and digital comparison tools generally and has criticised some of their practices. I'm not aware of a flight aggregator -specific investigation, perhaps there should be one.
Many businesses and people complain about all these laws, regulations and investigations but they exist partly because some traders have taken advantage of consumers, to put it mildly, and those online can take advantage at scale. Their behaviour advantages themselves to the disadvantage of the consumer.