The Eiffel Tower would be destroyed by an aircraft crash. Consider the WTC, which had an immense amount of protection around the central support columns, which were made of high-grade 1970's steel and concrete. The Eiffel Tower is constructed of 19th century riveted puddled iron, with no concrete. There isn't anything around the load-bearing frame of the Tower to protect it from impact.
If a jumbo jet were to impact the tower, say about 2/3 of the way up, at an oblique angle, the top of the tower would be sheared off, collapsing downward. The aircraft would be heavily damaged, cartwheeling into the ground beyond the tower as the damaged portion of the aircraft peeled away. The top of the tower would collapse downward, onto the base, which, weakened by shearing forces of the impact, would partially collapse. The two feet closest to the side of the impact would be most weakened, while it is possible that the third and fourth feet might remain standing if there is not enough weight to pull them down.