Lay is often used where lie is considered standard, as in "I'm going to lay down for a quick nap." The use, which dates to the 14th century, troubled no one until the 18th, but since then, people who care about such things have tried to teach the rest of us that a person lies, not lays, down.
LIE definition: 1. to be in or move into a horizontal position on a surface: 2. If something lies in a particular…. Learn more.
A lie is something that someone says or writes which they know is untrue. "Who else do you work for?"—"No one."—"That's a lie." I've had enough of your lies.
lie (laɪ) vb (intr) , lies, lying, lay (leɪ) or lain (leɪn) 1. (often foll by down) to place oneself or be in a prostrate position, horizontal to the ground
A lie is an assertion that is believed to be false, typically used with the intention of deceiving or misleading someone. [1][2][3] The practice of communicating lies is called lying. A person who communicates a lie may be termed a liar.
lie /laɪ/ vb (lies, lying, lay /leɪ/, lain /leɪn/) (intransitive) (often followed by down) to place oneself or be in a prostrate position, horizontal to the ground
If something lies unused, it is just sort of left to lie on the shelf (or wherever). If you let a sleeping dog lie, you're just letting him be right where he is — in the same position.
As fev says, "within" pretty clearly means that there is some range of time in which you must fill out the form. The potential ambiguity is because in "within 10 days before the flight", the following noun phrase "10 days before the flight" has a form that would generally cause it to be interpreted as a point in time rather than a range.