(NewsNation) — Congress on Wednesday will hold a hearing on unidentified flying objects or, as the Pentagon classifies them, unidentified aerial phenomena. But it’s not the first time the U.S. government has searched for answers about objects in the sky.

The hearings come after David Grusch, an Air Force veteran, claimed he had evidence of a secret program designed to retrieve debris from objects of “exotic origin.” Grusch claims there is reason to believe that debris is indeed extraterrestrial in origin.

Whether you prefer to call them UAPs or UFOs, there’s no doubt America has a long-standing fascination with mysterious flying objects. Here’s a look at how previous government investigations have been handled:

Project Sign, 1948

Project Sign began in 1948. The Air Force began collecting information on UFO sightings, concerned that they might represent a threat to national security.

The Air Force found the objects people were reporting were indeed real, but most had ordinary explanations. However, the military recommended continuing to investigate sightings and did not definitively rule out extraterrestrial origins.

Project Grudge, 1949

Project Sign evolved into Project Grudge in 1949. The project was an attempt by the Air Force to tamp down on UFO reports from the public and to reassure people that most unidentified objects had mundane explanations.

The Air Force also recommended ending the project the same year it began, because of the belief that official investigations only spurred public interest in UFOs. A report issued in August 1949 found there was no reason to believe the objects represented any advanced scientific projects and did not pose any threat to national security, whether it be from those outside our solar system or foreign adversaries on Earth.

Project Blue Book, 1952 – 1970

Project Blue Book was the Air Force’s next attempt to conduct a systematic study of UFOs. Cold War-era fears of advanced Soviet technology were a concern even as popular accounts of UFOs attributed them to visitors from beyond our planet.

Once again, the Air Force issued reports stating they determined the majority of reported objects could be identified and explained. Reports from Project Blue Book indicated there was no evidence of technology beyond what current science and technology could produce and no evidence of extraterrestrial origins.

Project Blue Book consultant J. Allen Hynek would later go on to refute the Air Force report, and said many of the explanations offered were not legitimate and there was a need for further study. Hynek said both Project Blue Book and the CIA’s Robertson Panel were created with the intent to disprove the possibility of UFOs and both discounted any evidence contrary to that position.

Robertson Panel, 1953

A sharp increase in UFO sightings in 1952 led the Central Intelligence Agency to conduct its own UFO investigations. The Robertson Panel said most UFO sightings could be explained by people misidentifying mundane objects but also recommended the agency continue monitoring sightings.

The panel also recommended the CIA keep their interest secret and launch a campaign to educate the public and reduce interest in UFOs. The panel feared the volume of UFO reports from the public could overwhelm government agencies and legitimate reports of national security threats could get lost in the shuffle.

Congressional Hearings, 1966

A string of UFO sightings in Michigan led former President Gerold Ford, then serving in the House of Representatives, to call for congressional hearings on the subject. Officials explained the sightings away as mistaken identification of the moon and stars or the result of swamp gas.

The hearings resulted in the creation of the Condon Committee, a civilian group based out of the University of Colorado. The group’s report, released in 1969, found no justification for the study of UFOs and recommended against government efforts to track or study sightings. A congressional hearing on the report resulted in the end of Project Blue Book.

Roswell Report, 1994

Arguably the most famous UFO sighting, the government initially explained the 1947 Roswell incident as debris from a weather balloon.

In 1994, Rep. Steven Schiff (R-NM) requested the Government Accountability Office look into the official explanation. They ordered an Air Force review, which concluded the weather balloon story was indeed a cover-up, but it wasn’t aliens the government was hiding. The debris was attributed to Project Mogul, a secret military surveillance program using high-altitude balloons.

Advanced Aerospace Threat Identification Program, 2007

Sen. Harry Reid, D-Nevada, pushed for the creation of the program to study what the government began calling unidentified aerial phenomena to avoid the stigma of the term UFO. Run by the Department of Defense, the program focused on sightings from military personnel and the department claimed it ended in 2012.

However, those involved with the program claim it continued after funding ended in 2021 with support from the Navy and the CIA.

The Unidentified Aerial Phenomena Task Force, 2017

Running from 2017 to 2020, the Office of Naval Intelligence program collected accounts from military personnel who experienced strange sightings. In 2021, the program issued a report and the Pentagon confirmed, for the first time, that videos showing strange objects were authentic.

The task force was unable to identify 143 of the 144 objects sighted but said there was no evidence to categorize them as extraterrestrial in origin. The group became the All-domain Anomaly Resolution Office in 2021 and continues to track military sightings.

Congressional Hearings, 2022

In 2022, Congress held the first public hearings since the 1960s, which centered around the UAP task force report. In the hearing, officials revealed the database of sightings had expanded to more than 400 encounters and most could not be classified as known physical objects. The objects were also not believed to be part of any secret U.S. government programs or made by other countries.

Not all lawmakers were satisfied with the results of the hearings, suggesting the military was continuing to engage in a cover-up.