Originally Posted by
Globaliser
Not all airlines participate in Global Distribution Systems, which are the source of EF's information. In particular, low-fare airlines very often do not do so, as part of their business model.
In addition, Delta have prohibited EF from showing their flights. DL operated flights that are codeshared to another airline do appear as that other airline's flight (with a notation that it is DL operated) but apart from those no DL flights.
DAK