1. Approval: Airport construction needs to be approved by many departments, including civil aviation, military and local governments. If there is a problem in the approval process, the airport construction may be delayed.

2. Capital: Airport construction needs a lot of capital investment. If there is a problem with the source of funds, the project may be postponed.

3. Technical problems: Airport construction involves technical problems in many fields. If the technical problems are not solved properly, the construction progress may be slow.

4. The preliminary work is not completed: the airport construction needs to complete the preliminary work such as site selection, planning and design. If these tasks are not completed, it will also affect the airport construction.

The above is only one of the possible reasons, and the specific situation needs further understanding and confirmation.