It hasn't, because anyone who watches the hearings quickly realizes none of the witnesses actually witnessed anything that they think could be aliens...
There's a guy who won't say anything, a guy who claims to have (at best) secondhand knowledge that proof exists but won't deliver anything or anyone's names, and then a retired pilot who just says he saw something that he can't explain.
The hearing is a dog and pony show run by some of the dumbest people in our government. And virtually all their questions are some type of hypothetical about "what if it was aliens, shouldn't we make that public?"