Ground Services vehicles and jetways are dependent on two factors:
- Aircraft properties
- Parking Type properties.
For each aircraft properties, there are a few parameters that’s set such as the Type of pushback tug, between a large tug or a smaller one. There’s also parameters whether Ramp and Jetway, and Baggage vehicle and catering is available to that aircraft or not. This makes up the first set of parameters that the sim uses to check what vehicles to spawn or not.
The second parameter, is the parking type. MSFS has 6 distinct parking types:
- Gate (Heavy)
- Gate (Medium)
- Gate (Small)
- Ramp GA (Large)
- Ramp GA (Medium)
- Ramp GA (Small).
The Gate types all have everything that airliners need available. This includes Jetways, Pushback Tug, Baggage Handling, and Catering. The only difference between the Heavy, Medium, and Small is merely on the size of the parking, with Heavy can fit aircrafts with larger wing-spans while if you spawn a 787 to Gate Small there’s a potential for the wings to clip through the sides.
Ramp types however, are a bit more restrictive. Ramp GA (Large) have Pushback Tug, Baggage Handling, Catering like the Gate types. The only difference is that it doesn’t have Jetways, but instead it has Ramp stairs for large airliners available.
Ramp GA (Medium) however, doesn’t have Ramp stairs anymore, and I believe it also doesn’t have catering car, but it still have baggage and pushback tug. (I could be wrong though).
Ramp GA (Small) is the smallest parking type, that doesn’t have anything. (maybe it has pushback tug, but only the small tug, not the large one).
Now, MSFS needs to have both parameters match to be able to spawn the ground vehicles. You can have catering car spawn on Gate parking type on the A320, while you don’t have it spawn when parked in a Ramp GA (small) type. But vice versa could also behave the same way, that even though Gate Parking type has catering car, if you spawn a small Cessna 172 on Gate parking type, the catering car won’t spawn because the aircraft parameter doesn’t have it available.
So when it comes to your issue. It just depends on which parking type that you went to after landing. If you go to the Ramp GA (medium or small) type after landing, you won’t get the staircase because the staircase do not spawn on those parking types. You need to park to Ramp GA (Large) parking type in order to have the staircase.