Difference between "seems" from past evidence and "seems" from current experience


Part way through [this
question](https://japanese.stackexchange.com/questions/52269/choosing-
between-%E3%81%9D%E3%81%86%E3%81%A0-%E3%82%88%E3%81%86%E3%81%A0-and-%E3%81%AF%E3%81%9A%E3%81%A0)
I got a bit side-tracked. I'll try and express my problem better here.

I think that the conclusion to the previous question was that 飛行機が混みそうです means
"It seems the plane will be crowded". Here 'seems' implies that after
examining the evidence (e.g. of previous flights) there is a reasonable
probability that the plane will be crowded.

How would I translate "The plane will seem crowded"? In this case 'seem' is
expressing visual perception while **on** the plane. e.g. it will seem crowded
because all the passengers that have checked in are very fat and will take up
a lot of room.

Would that also be 飛行機が混みそうです? Do I just have to infer the meaning from
context or is there a different grammatical construction?




"飛行機が混みそうです" can be rightly translated to "It seems the plane will be
crowded," but no, it won't do as a translation of "The plane will seem
crowded." Here's why I think this is so:

In "飛行機が混みそうです", the そう can be thought of as pulling semantic double duty. It
serves two roles: one of denoting inference (corresponding to "It seems" in
the good translation) based on evidence, visual and/or otherwise; the other of
denoting future-time reference with regard to the action/state expressed by
the verb it attaches to (corresponding to "will (be crowded)").

With "The plane will seem crowded," however, "seem" indicates _not_ inference,
but _appearance_ , and "will" indicates the speaker's belief about a future
event/situation. This set of meanings you cannot assign to the (連用形 + )そう.
It's not in its job description.

So, how do we go about translating "The plane will seem crowded."? Maybe like
this:

> (あの体の大きな人たちが乗ったら、)飛行機が混んでいるように[見える/感じる]でしょう。

Or we can use そう this way:

> (あの体の大きな人たちが乗ったら、)飛行機が混んでいるように[見え/感じ]そうです。




この飛行機は混みそうだ can be used when the plane is not crowded now but you think it
will be crowded, based on some evidence. What you've just seen with your eyes
safely works as an "evidence". This can be said even after you've gotten on
the plane.

For example, you've just boarded a plane, and see there are still a lot of
vacant seats. A while later, you suddenly notice a large group of sumo
wrestlers boarding. In this case, この飛行機は混みそうだ is a natural sentence. Since
you're already on board, you may also say この飛行機は混んできそうだ (See: [Difference
between -ていく and -てくる](https://japanese.stackexchange.com/q/676/5010)).

この飛行機は混んでいそうだ or この飛行機は混んでそうだ (colloquial) can be used when you don't know if
the plane is crowded now, but you think the plane should be currently crowded
based on an evidence. For example, when you are in a long waiting line for
boarding that does not proceed even after the departure time, you can say
この飛行機は混んでそうだ.

