Fly the Line: Short Haul Edition is primarily focused on simulating a short-haul airline pilot's lifestyle. You can read the product description of Fly the Line: Short Haul Edition on the product page here: https://www.justflight.com/product/fly-the-line-short-haul-edition
Additional features beyond the scope of the product, such as cargo airlines and bush flying, are on the developers' radar for future versions of Fly the Line, however, they aren't natively supported in Fly the Line: Short Haul Edition.
When generating schedules, a message will appear on the world map as a warning if too many routes are selected. The more routes that are selected, the longer the schedule generation will take. The exact time it will take to generate schedules will also vary based on PC specs. We would recommend taking advantage of the advanced options when generating schedules and keeping the number of schedules generated to a maximum of approximately 50.
One of the main aims of Fly the Line is not to restrict your choice of aircraft types. This removes the sometimes tedious grind that can often be required in other career mode products, which acts as a barrier that prevents you from flying the aircraft you want to fly.
Mark - Just Flight