Project Blue Book
Gillen starred in The History Channel's series "Project Blue Book". He plays Dr. J. Allen Hynek, a brilliant and underappreciated college professor who is recruited by the U.S. Air Force to spearhead an operation named Project Blue Book. He is joined by his partner Air Force Capt. Michael Quinn as they investigate UFO sightings around the country. "Project Blue Book" was renewed for a second season in February 2019 amid strong ratings for the series, which is averaging 3.4 million viewers in L+3.