I had the experience once of having flight 2 and flight 12 and flight 22 all operating on the same route very close together. ATC asked me to amend the flight numbers of at least 2 of them to show the a/c rego instead of number. Then, the next day had flight 2 and flight 22 - close together and same dest. Okay I thought, I will use their rego's instead. What do you reckon the chances of having ECHO BRAVO CHARLIE and ECHO CHARLIE BRAVO ? Oh yeah, it happened. Simple fix but - give me a break .