My brain isn't working, I'm tired more often than usual, so I watch something like this and get myself to write about it for a week. Which is especially odd because I liked it quite a lot. So, in lieu of my writing an actual brief review, some random comments so I can move on.
The overall production is just stunning. There is a real vision behind it, and it doesn't look like anything else. There are two basic sites, one of which is Earth and the other of which is probably Heaven. Heaven is in black and white ... it's a lovely black and white, not drab, but it's interesting that the color exists on Earth and not in the promised land. The most quoted line in the movie is when Conductor 71, something of a guide/angel, goes to Earth, appreciates the colors, and remarks, "One is starved for Technicolor up there." The movie is a fantasy that doesn't always play like a fantasy ... David Niven's character jumps out of a plane without a parachute, seems to survive, battles with the powers in Heaven who want him to be dead as was planned ... you know you're watching a fantasy, but he also has a brain injury that requires surgery, and there's a suggestion that the entire movie after he jumps out of the plane is him in his head as he is being operated on.
The key to grounding this is the romance between Niven and Kim Hunter as an American radio operator who "meets" him on the radio as he talks to her prior to his leap. Hunter is very believable ... you believe she fell in love with a voice, and you can definitely see why Niven's character fell in love with her. This was Hunter's first starring role, leading to a strong subsequent career ... an Oscar for Stella in A Streetcar Named Desire and a Daytime Emmy for the soap opera The Edge of Night, along with important appearances in the first three Planet of the Apes movies.
But really, it's the look of A Matter of Life and Death that lifts it above the norm. It needs to be seen to be believed. #144 on the They Shoot Pictures, Don't They list of the top 1000 films of all time.