Артур Хейли: Runway Zero-Eight

Although airlines throughout the world operate on Greenwich Mean Time so far as their crews are concerned, the journey of over 1,500 miles from Winnipeg to Vancouver involves three local time zones: Central Time, Mountain Time, and Pacific Time. This double resetting of the clock each time to put the hands back an hour, would be chronologically confusing in the story which follows. One standard time, therefore, has been assumed throughout.

It is hardly necessary to add that the events, the airlines, and all the persons mentioned are entirely fictitious.