The opening scene includes a shot of a TV newsreader saying the line "Achilles 6, the mission that was to inaugurate man's first permanent station on the moon." In a later flashback. Mission Control is shown on the TV screen, while he reads the line, off camera.
Brunel is reading Morlar's Diary. In it it says "Zonfeld, if she only knew" A moment later Morlar's voice is saying "Zonfeld, if only she knew".
The line before "Jesus is the in-thing" is totally different in the diary and in Morlar's voice.
About 20 minutes into the film, Lee Remick is sitting at her desk talking to the inspector. Her hair is loose, i.e. not pulled back. A little later she is still at her desk talking to the inspector and her hair is held back with a clip.
Bells, that should weigh tons, bounce off the ringers' heads.
Real stone cathedral walls would crack along the edges of the individual stones, not split across them, as do these fake ones, that are obviously a single panel, painted like individual stones, split, and debris pushed through the "cracks".
From early on in the film, there is not a shred of "Doctor - Patient privilege". It is totally illegal for a psychiatrist to tell anyone about what is said in confidence to anyone; especially the police.
As Inspector Brunel watches the TV news a close-up of the screen reveals that the caption saying "Minster Cathedral" is actually stuck on to the TV screen rather than forming part of the TV picture. The letters cast shadows on to the glass.
When the 747 explodes after hitting the office block, the ends of the wings can be seen still suspended where the wires failed to detach.
During the end scene when the cathedral is collapsing, large pieces of masonry are falling about the place. However during the panic you can clearly see people pushing on the blocks of stone. However they move very easily. They were made of plastic, Plaster of Paris, polystyrene and Papier-mâché.
As the cathedral comes crushing down, people watch the disaster live on TV. However, what they watch is a heavily edited footage, including various cuts, jumps, close-ups, etc. This would not be possible in a live broadcast.
When passing the 747 wreckage in the street, a thrust vector nozzle from a Harrier Jump Jet is prominent.
When Morlar visits a fortune teller, the boom mic is visible above the fortune teller's head.