Senator Chuck Schumer of New York, the majority leader, is pushing legislation to create a commission with broad authority to declassify government documents about U.F.O.s and extraterrestrial matters, in an attempt to force the government to share all that it knows about unidentified phenomena.
The measure offers the possibility of pushing back against the conspiracy theories that surround discussions of U.F.O.s and fears that the government is hiding critical information from the public.
The legislation, which Mr. Schumer will introduce as an amendment to the annual defense policy bill, has bipartisan support, including that of Senator Mike Rounds, Republican of South Dakota, and Senator Marco Rubio, Republican of Florida, who has championed legislation that has forced the government to release a series of reports on unidentified phenomena.
Support in the House is also likely. On Wednesday, the chamber included a narrower measure in its version of the annual defense bill that would push the Pentagon to release documents about unidentified aerial phenomena.
(While the government has agreed not to call mysterious sightings U.F.O.s, various branches and agencies disagree on whether to refer to aerial phenomena or anomalous phenomena.)
The Senate measure sets a 300-day deadline for government agencies to organize their records on unidentified phenomena and provide them to the review board.
President Biden would appoint the nine-person review board, subject to Senate approval. Senate staff members say the intent is to select a group of people who would push for disclosure while protecting sensitive intelligence collection methods.
Interest in U.F.O.s has always been high, but it has grown even more since a collection of videos showing unidentified phenomena recorded by military sensors was made public and naval aviators described hard-to-explain events while on training missions.
Some of the videos released by the Pentagon have been explained as optical illusions or drones, but others remain unexplained and the object of much speculation. Under pressure from Congress, the Pentagon and intelligence agencies have gathered hundreds of reports of unexplained phenomena. Officials have said most of the unexplained incidents are airborne trash, Chinese spying efforts or errant weather balloons. American officials have repeatedly said that none of the videos or other material they have collected appears to be evidence of alien visitation.
It is hard to know how many unreleased documents exist in government archives. Intelligence agencies have said repeatedly that they have released the material they have. Their freedom of information offices are constantly deluged with requests for material on U.F.Os., only to be met with responses that the archives have been released.
Still, more recent work, particularly by the Pentagon, has not been made public, and the reticence of some government agencies to produce records has frustrated both Democratic and Republican lawmakers, Mr. Schumer’s staff members said.
For example, various Pentagon task forces have conducted extensive studies on videos taken by naval aviators and other military personnel that have remained secret. Some work on the videos has been released, including at a recent NASA meeting. In some cases, officials believe disclosures could reveal the capability of classified optics and sensors. But in cases in which no formal conclusion has been reached, officials have been reluctant to share information on their deliberations or theories.
It is the reluctance to share all that is known about the incidents that are not completely understood that has fueled endless speculation on social media, in television specials and public debates.
The new legislation is modeled on the commission that oversaw the release of information about John F. Kennedy’s assassination. That legislation, passed in 1992, has been imperfect, and both the release and withholding of documents have continued through the Biden administration.
Still, the Kennedy assassination review board has forced the release of thousands of pages of documents, and lawmakers believe the approach could work here.
Under Mr. Schumer’s legislation, the president could decide to delay material the commission has chosen to release based on national security concerns. But the measure would establish a timetable to release documents and codify the presumption that the material should be public.
“You now will have a process through which we will declassify this material,” said Allison Biasotti, a spokeswoman for Mr. Schumer.
Government officials have repeatedly said they do not have the remains of a crashed alien spacecraft or any manufactured material of extraterrestrial origins.
Those assertions have been challenged by some former officials who believe the government is not divulging all that it knows. The legislation would likely force more details of the government’s study of unknown materials to be released, but it also gives the federal government the power to claim any crashed spaceships in private or corporate hands, however unlikely that such things exist.
Mr. Biden, unlike former President Barack Obama, has not directly addressed the issue of unidentified phenomena. But Mr. Biden did order two unknown objects and a Chinese spy balloon to be shot from the sky. Afterward, the president said that he would not apologize for shooting down the spy balloon and that the United States would continue to adapt its approach to dealing with unknown objects.
Karoun Demirjian contributed reporting from Washington.