Answer:
(Fatwa: 1462/1183/L=1430)
As per the Shariah, it is impermissible to pay insurance tax while purchasing air ticket, but it is compulsory for buying a ticket; therefore in compulsion it is regarded lawful. You only sell the ticket, there is nothing forbidden involved in your work, you are not responsible for what the airline does like offering wine and showing film; therefore you can work in the travel agency.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband
