Both flights are Transavia flights, and are sold on Transavia's website as connecting flights.
But connection is "guaranteed" by Dohop.
Is this legal?
Both flights are Transavia flights, and are sold on Transavia's website as connecting flights.
But connection is "guaranteed" by Dohop.
Is this legal?
The economy of pricing flights is very complex which is why there are sites that try different strategies to show a lower price than elsewhere. Effectively, your business is with the online-travel-agency (OTA), they happened to have sold you two tickets from the same airline. Given these are two tickets, the airline is not responsible for ensuring the connection, so the premise of your question is unlikely to be correct. Transavia did not sell you two connecting flights without taking responsibility, Dohop did and they are claiming to take responsibility. Since they are not the airline though, the recourse they have to take responsibility are not the same.
Airline ticket pricing is influenced by a huge number of factors. Suppose you are traveling from city A to city B. Often, the cost of the direct flight between these cities will be highest at a certain level of service because such flight is the fastest and least risky. For the convenience, some people prefer to pay the higher price. Others, are more concerned with cost and would not mind flying from A to an intermediate city C and then onward to B. The route takes longer and there is a chance of delays causing a missed connection, plus time lost in transit. There is clearly more hassle this way and so such flights typically cost less than a direct flight. Airlines regularly offer both these options. In the example you gave, it is very likely that Transavia offered such connecting flight.
To give you an even cheaper flight, Dohop figured out that Transavia priced the direct A-to-C and direct C-to-B flights lower than the connecting A-to-C-to-B route. This happens frequently due to market demands for some routes. So, instead of buying the connecting flight, Dohop acted as an agent to sell you two flights. It could have been from different companies but coincidentally both were from the same airline.
By offering these two flights together, you are able to get an even lower price than the connecting flight. At the same time, this introduces a risk to you as it could be that one of your flights gets sufficiently delayed that the connection is not possible or that it could be cancelled entirely. You could have bought these two tickets without Dohop but they are offering to handle some of the risk for your business. If no issue occurs, then you got to pay the lower price and Dohop pockets the commission. Like insurance, this is the most scenario everyone hopes for! Should an issue occur, it will be up to Dohop to pay for correction. There are different ways it could be done but essentially they will either pay for rebooking or a new flight. This will most likely introduce delays at the very least and you may lose a few days at your destination due to flight availability. How inconvenient the change will be is anyone's guess, it can vary greatly depending on circumstances.