Is money earned from a pilot's job unlawful (haram), and is working in it considered a grave sin, knowing that many Muslims work in it, and for the questioner, it is a lifelong dream?

There is no objection to a person working as a pilot if they are safe from directly committing a forbidden act or assisting in it, such as being in seclusion with a foreign woman (khalwa (definition)) or serving alcoholic beverages. Some scholars have prohibited working if the company serves alcohol on the plane, while others have permitted working with the obligation to denounce the forbidden act. The safest approach is to search for a company that does not serve alcoholic beverages, while also being careful to avoid other forbidden acts.