Michael Caine

Brad Crane

Katharine Ross

Capt. Helena Anderson

Richard Widmark

Gen. Thaddeus Slater

Richard Chamberlain

Dr. Hubbard

Olivia de Havilland

Maureen Schuester

Ben Johnson

Felix

Lee Grant

Anne MacGregor

José Ferrer

Dr. Andrews

Patty Duke

Rita

Slim Pickens

Jud Hawkins

Bradford Dillman

Maj. Baker

Fred MacMurray

Maj. Clarance Tuttle

Henry Fonda

Dr. Walter Krim

Cameron Mitchell

Gen. Thompson

Christian Juttner

Paul Durant

Morgan Paull

Dr. Newman

Alejandro Rey

Dr. Martinez

Don 'Red' Barry

Pete Harris

Elizabeth Rogers

Woman Scientist

Ernie F. Orsatti

Duty Officer

Patrick Culliton

Sheriff Morrison

John Furlong

Cameraman

Chris Petersen

Hal

Steven Marlo

Pilot #1

Arthur Space

Engineer

Chuck Hayward

Standby Engineer

Ken Clayton

Dr. Moore (uncredited)

Bob Harks

Townsman (uncredited)

Lawrence Moran

Colonel's Son (uncredited)

Monty O'Grady

Briefing Guest (uncredited)

John Otrin

Wild Lines (uncredited)

Leoda Richards

Briefing Guest (uncredited)