Best thriller movie mistakes of 1970
Continuity mistake: Burt Lancaster is sitting in his car at the end, and he asks the tower if he can listen to the radio traffic for the incoming plane that's landing. The tower replies "Sure, it's on frequency 117.1". Burt then tunes the dial on his receiver to 171, not 117. 170 is blatantly written under the dial in bold type.
Revealing mistake: A Nineteenth century social occasion is taking place at a mansion in the evening. The lead female vampires servant arrives by horse in front of the mansion and in the background you can see some modern tennis courts with metal gates and fences. The nets have been removed but the appearance of the courts can still be seen.