Your observation is partially correct. The language does make a distinction when you're defining new functions: you must use the "inflight" keyword annotation to define an inflight function, and most un-annotated functions are assumed to be "preflight". (The top-level scope of every Wing program has a preflight phase).
But at _call sites_ no distinction is made. We don't have have a different calling convention between calling preflight/inflight functions because the compiler uses type checking to enforce that inflight functions can only be called in inflight scopes, and preflight functions can only be called in preflight scopes. Scopes are lexical, meaning you can automatically assume when you see `inflight () => { ... }` or `inflight foo() { ... }` that all code inside that block is executed inflight, i.e. at runtime.
The neat thing here is if you're writing code to access a method on a class (typing `obj.`), your IDE's auto-completion will only show you the methods available to you based on the scope you're in. There's a short 10 second clip showing this here: https://twitter.com/rybickic/status/1720168675641102803
We've prioritized LSP support while designing the compiler to help out with this.