I have wondered several times about this and now seeing this question Can two different planes share the same flight number? I decided to ask:

In general in our mind we think of flights number as something unique (at least I did). An ID. Often journalists mention the flight number when they want to refer to a particular event (a crash, a forced landing, whatever) which reinforces the idea of uniqueness.

From what I read a flight number:

  • clearly does not represent a plane
  • does not represent a unique flight in particular (since the same flight number is commonly reused several times to represent the same flight at the same time in different days)
  • does not represent a route (since the flight number can be used on several routes)

What is its use than and does it represent? What makes it unique and usable? can there be, for instance, the same flight number at the same time in different routes?

  • 1
    Since the same flight number is commonly reused several times to represent the same flight at the same time in different days I have never encountered any occurrence where this was not the case. For example, currently ANA's flight NH217 goes every day from HND to MUC, and will continue to do so until ANA decides to drop this route (and then possibly reassign this number to some other route), or maybe decides to retire this number if some major incident occurs on it. – fkraiem Nov 5 '15 at 13:20
  • 2
    A particular flight can be identified by giving a flight number and a date. For example when you read about "flight MH370", it may be obvious (depending on context) that it is in reference to flight MH370 of March 8, 2014, in the same way that when you read about "September 11", it may obviously refer to September 11, 2001. – fkraiem Nov 5 '15 at 13:23
  • @fkraiem that seems obvious to someone knowing the gregorian calendar and the September 11 event. But it's not that obvious if you either use a different calendar or are not aware of the event. The common person is not aware of the codes used in aviation. I thought these were unique for a very long time. – nsn Nov 5 '15 at 13:33
  • Yes, perhaps I should have said "it is meant to be obvious". What I meant was that whoever says or writes this expects that the reader knows what is meant even if some information is missing, although of course it may not always work, for various reasons. – fkraiem Nov 5 '15 at 13:42
  • Note that what I said above about flight NH217 was just an example illustrating what is in my experience common practice. As I said, I have never encountered a flight which did not operate in such a way, but some may (and probably do) exist since, as the answer in the duplicate question says, there is no rule governing the usage of flight numbers. – fkraiem Nov 5 '15 at 13:54

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