The three major US airlines that fly Boeing’s Max 737 have announced that the jet’s return will be pushed back yet again.

On 13 February, Southwest Airlines released a revision to its flight schedule, removing the planes from the flight schedule through 10 August, and on 14 February, American and United followed suit, pushing to 18 August and 4 September, respectively. The Max was previously slated to return in early June on all three carriers.
Southwest said in a statement that while the change would eliminate about 371 weekday flights out of more than 4000 flights daily, removing the Max from scheduled service now would reduce last-minute flight cancellations and disruptions during the busy summer months.

In its announcement, American said that it remains in continuous contact with the Federal Aviation Administration, Department of Transportation, and Boeing, and this decision was made based on the latest guidance. As a result, the carrier said it would pull some 140 flights a day during the summer, or approximately 4300 a month, according to the AP, and United would lose 80 flights a day, or 2500 a month, during the same time period.
The planes have been grounded since March, after two crashes cost 346 people their lives. Originally, the Max's delayed return was attributed to the lengthy process of updating the flight-control software that was partially to blame for the crashes, but as the New York Times reported in January, the issues with the jet run deeper than previously thought, from concerns over critical wiring to potential vulnerabilities in and around the engine.

“The FAA and Boeing are analyzing certain findings from a recent review of the proposed modifications to the Boeing 737 Max,” FAA spokesman Lynn Lunsford told the Times. “As part of its continuing oversight, the agency will ensure that all safety-related issues identified during this process are addressed before the aircraft is approved for return to passenger service.”
For its part, Boeing said in a January statement that the jets would likely be reintroduced in mid-2020, an estimate that “accounts for the rigorous scrutiny that regulatory authorities are rightly applying at every step of their review. Returning the Max safely to service is our number one priority, and we are confident that will happen.”