Section 43(1) FPG applies where a person states at border control that they are a transit traveller. Stay in the transit area must be refused if re-departure does not appear secured because of specific circumstances. A general uncertainty does not replace that statutory connection.
A separate trigger exists where, after the first stay in the transit area, the next state refuses entry and sends the person back to Austria. The review therefore follows the order of travel, the decision of the next state and the return.
The transit safeguard may also apply where the required airport transit visa under the Visa Code is missing. Route, nationality, visa requirement and the documents presented must be considered together. This is the transit case under section 43 FPG, not a general answer to an entry-ban question.