Hello, our company process customers' personal data for the Client. We are providing consulting services for the customers, including consulting on air transportation issues. If a particular customer asks to transfer his/her personal data to a third party service provider which deals with these issues to assess the possibility of entering into a contract with such customer, this third party service provider would be a controller under GDPR before it enters into a contract with a customer? Or he would be in some different role? Thanks.
Yes, it would be a data controller even before entering into a contract, because the third-party service provider will be free to decide the purposes and means of the processing of personal data belonging to the potential customer.
Here you can find more information on the role of processor and controller: