Is it permissible to open a travel agency affiliated with a Hajj and Umrah campaign to issue airline tickets to all countries of the world, or should it be restricted to issuing tickets only for the Two Holy Mosques and for countries whose citizens work in the UAE?

It is permissible to open a travel agency and sell tickets, provided that its work does not involve assisting in a forbidden act, such as selling tickets to someone known or strongly suspected of traveling for illicit purposes, or booking in places of corruption. The evidence for this is the Almighty's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). Sheikh Ibn 'Uthaymeen was asked about selling tickets in installments with an increase, and he permitted it, but he warned against traveling to countries of corruption. He also pointed out that some agencies facilitate travel to entice the foolish, and he emphasized that traveling to places of corruption is fundamentally impermissible. Consequently, there is no harm in opening the office and selling tickets except to those whom you know or strongly suspect are traveling for corruption. As for those whose circumstances you are unaware of, there is no harm.