Southwest Airlines Co., the largest operator of the grounded Boeing Co. 737 Max, said the discovery of a new safety issue with the jetliner is extending its absence ¡°well beyond¡± what was hoped, forcing the carrier to reassess its schedule for the rest of the year.

The latest problem, ¡°unfortunately, is going to delay the time-line for returning the Max to service,¡± in early October, Chief Executive Officer Gary Kelly told employees Monday. ¡°That¡¯s very disappointing.¡±

Separately, American Airlines Group Inc. suspended a daily round trip between its hub at Dallas-Fort Worth and Oakland, California, because of the Max grounding.