Is it permissible for one person to use two different flight tickets from two different sources, knowing that one is for attending a conference and the other is for a vacation?

The ruling on obtaining two flight tickets from two different entities depends on the conditions set by the granting entity, based on Allah's saying: (O you who have believed, fulfill [all] contracts) and the Prophet's saying: "Muslims are bound by their conditions." If neither entity stipulates the absence of another ticket, and the ticket is granted as a form of ownership, then it is permissible to take both tickets and dispose of the value of one of them. However, if the granting of the ticket is conditioned upon the absence of another ticket, then it is not permissible to receive it except from one entity.