You should investigate and, if not already, become familiar with revenue management. https://w3.accelya.com/blog/airline-revenue-management-strategy-101-its-all-about-alignment
This will help you to understand the relationship between air transport passenger /cargo data and financial costs/revenue.
Historic data provides some guidance for predicting future trends.
If you are in the EU https://ec.europa.eu/eurostat/statistics-explained/index.php/Air_transport_statistics
Many airlines are retiring old, inefficient aircraft. The future may not require as much capacity, as much as lower emissions and fuel types.
For airports;
You will need to understand runway length vs T/O distance, taxi/apron widths vs wingspan and most importantly weight & emissions; as this will determine airfield/landing/parking costs.
Quick and dirty: number of annual passengers divided by load factor (e.g. 80%) equals annual seats; this amount divided by 52 weeks/year, by 2 (inbound or outbound pax), by 6 (days/week considering weekend as a single day) and by the number os seats/acft type will result in number of daily flts/day. Since the air transportation product is affected by the frequencies offered (the higher the better), consider a minimum of two daily frequencies a goal.