Delta on Saturday will begin Newark-Paris Charles DeGaulle Airport service, with a 6:50 p.m. departure aboard a Boeing 767-300ER. The first Paris/Newark flight will depart at 1:30 p.m. on Sunday.

In general, airlines avoid one another’s hubs, although Newark is a special case because it is not only a hub for United, but also a leading international gateway airport, where the rules of airline combat may be loosened because such airports tend to have large numbers of passengers who originate and end travel, as opposed to passengers who are simply connecting.