A former Canadian defence minister is heading a speaking tour about the alleged cover up of UFOs by world governments.

A crowd of about 400 people attended the "Disclosure Canada Tour" stop at the University of Calgary Saturday, to hear keynote speaker Paul Hellyer. Hellyer served as Canada's defence minister in the 1960s.

Hellyer and the other speakers on the tour want the government to release all the information they have on UFOs.

The 91-year-old Ontarian first spoke out about his belief that governments are covering up an alien presence in 2005. He says UFOs are as common in our skies as airplanes.

Hellyer said he's participating in the tour because he's committed to spreading the word about his beliefs.

"Much of the media won't touch it," he told CTV Calgary. "So you just have to keep working away and hope that someday you get a critical mass, and they will say, in one way or another, 'Mr. President or Mr. Prime Minister we want the truth and we want it now because it affects our lives.'"

The tour is scheduled to hit Vancouver on Sunday.