Yes, the system can be set up so that employee bookings need approval from a manager or travel coordinator before they become final. When an employee searches for and builds a trip in the portal, the booking can be held in a pending state instead of being confirmed right away. A designated approver then sees the booking request, can review the trip details and the cost, and can either approve it to move forward or reject it if it does not fit the company policy or budget.
How this works depends on how you want to structure your approval chain. You might have every booking go to one central person, or you might set different approvers for different departments or cost centers. Some companies also set automatic rules so that bookings under a certain price approve themselves, while anything more expensive needs a person to look at it. The system can send notifications to the approver so they know a booking is waiting, and can remind them if approvals are sitting too long.
Keep in mind that the approval process does add a step between when an employee wants to travel and when their booking is locked in. If you need instant confirmation, approval workflows may slow things down. You should also decide whether employees can see prices from all suppliers or only the ones your company has negotiated rates with, since that affects what they are approving in the first place.
To set this up, talk to your system provider about your approval structure and how many levels of sign-off you need, so they can configure the right workflow for your company.