What is the ruling on benefiting from an airline ticket if the purchaser doubts the method of its booking, and whether it originated from stolen or hacked money, knowing that its cancellation and refund are not possible?

The fundamental principle regarding transactions with a Muslim is their presumed lawfulness. You are not obligated to investigate how they acquired their wealth, and doubts hold no weight. Sheikh al-Islam Ibn Taymiyyah stated that a Muslim must avoid usurped money if they are aware of its nature. If one knows that a person has stolen or usurped money, it is not permissible to take it from them in any way. However, if the status of the money is unknown, the default is that what a Muslim possesses belongs to them, and one should not harbor ill suspicions. If a man is known to have unlawful wealth, dealings with him should be avoided out of piety. However, there is no suspicion in dealing with a Muslim whose affairs are concealed (i.e., not openly known to be involved in unlawful earnings), and whoever avoids dealing with him has introduced an innovation.