ITC on Airfare if invoice booked through Travel agent

Hello.

Let's take a case where I have booked an airfare ticket through a travel agent who acts as a Pure Agent under GST.

Travel agent issues an invoice including Air fare, K3 charges (GST on air fare), his service charge and GST thereupon as separate line items.

How to avail ITC on air fare and service charge charged by Pure agent?

How to account for this invoice in the books of account to fetch GST ITC details in the name of two parties, viz. Airlines and Travel agent correctly?

Please consider that since, a travel agent acts as a pure agent, entire costs including air fare, service charge and GST thereupon needs to be paid to Travel agent only.