"Can"

I want to open a combination lock, but I don't know the combination. Can I do it? There is some sequence of numbers which I can enter, and which is such that if I enter them it will open. So it seems I can. On the other hand, I can't fly a plane. Yet there is a sequence of button presses and movements of levers which I can make, and which is such that if I enter them the plane will fly.
It seems, thus, that the thing to say is that there is something which I can do, which is such that if I did it, the lock would open, and would open as a result of what I did, but nonetheless I can't open the lock.
But now suppose that I try to open it. I enter a sequence of numbers at random. And I get lucky: the sequence is right, and the lock is open. But if what I said above is correct, then it seems that I should say: "I opened it, even though it wasn't the case that I was able to open it." And that sounds weird.
Dan Johnson suggested to me that "can" is context-sensitive, and the context shifts when you open it. Maybe I should say: "Yes, I was able to open it, given my luck"?
Or maybe the thing to say is this. The subjunctive conditional

1. Were I to try to open the lock, I would happen to enter the correct combination

is true at some worlds and not true at others. At the worlds where it's true, I can open the lock, by using the obvious method for opening the lock: trying. At the worlds where it's false, I can't open the lock. The world where I do enter the correct combination when I try to open the lock is always a world where (1) is true. If subjunctive conditionals have non-trivial truth values (which basically means: either Molinism or determinism holds), then some of the worlds where I don't try to open the lock are worlds where (1) is true and some of them are worlds where (1) is false. So at some worlds I can open it and at others I can't, and before I try, I can't tell which world I'm in. On the other hand, if subjunctive conditionals don't have non-trivial truth values, and my choice of numbers would be indeterministic, then in the worlds where I don't try, (1) is not true (either false or nonsense), and in those worlds I can't open the lock.