A golf flight or tournament flight refers to a group or grouping for golf events. It's up to the tournament directors or golf event administrators to form the groups in whatever way they deem appropriate. Golf flights or groupings could be by USGA Index, course handicap (for course being played), age, previous round gross score, previous round net score, school grade, city of residence, etc. Most often a golf flight or tournament flight consists of players with similar handicaps. Tournament flighting, depending on the handicap range of the participants, might be along these lines:
The handicap ranges for the various flights are up to the tournament or golf event directors. Naturally, if a tournament is basing flights on a World Handicap System Index or Course Handicap, each player must have some sort of legitimately derived Index or handicap. Why would you want to flight a tournament using handicaps? If the competition is gross strokes - the actual strokes it takes a player to hole out - you would want players of comparable playing ability competing against each other. After all, it would not be a fair competition if a 20 handicapper was competing against a 5 handicapper. You could have a winner in each flight who had the lowest gross score. A tournament could also have an overall net score winner ignoring the flights since a net score evens the "playing field" using player handicaps.
Flight designations can vary. Some might use alphabet letters as above. Golf flight designations could be numbers, colors, names, etc. You've probably heard of "Championship Flight" and other tournament flight designations.
Golf tournament flighting can be a pain in the neck; especially when you are doing it under the gun (people watching over your shoulders). If you've got a computer program that flights quickly, accurately and easily, that's the way to go.