The graph shows the sum of distinct fa_idents per day in November for the top 100 airlines. The area marked “1” has a gap because my code was not running and I did not collect any schedule data for that period.
The area 2, however, shows that there were an unusually high number of flights scheduled (unique flights identified by unique fa_idents). I believe the problem is that one flight number got multiple fa_idents, for example DLH118 on Nov 8 or 9.
Is there a good reason this happens? And if it does happen, should I be using ident in combination with date rather than fa_ident to identify unique flights?