It seems like it’s used for both! The various dictionaries on Weblio define it as “nonstop voyage” or “sail direct” or other boat related definitions actually before the plane related definitions. The example sentences are a fairly even mixture of boats and planes.
Kotobank says 「船または飛行機が、途中でどこへも寄らず、直接目的地に航行すること 」mentioning boats before planes too.
The “this” in the last part, to me, is “this word when used with flying things” and since the the previous part wasn’t exclusive to flying things (“like with flying things”) we can infer that it applies to other things too.
And then they outright show you it can in the example.