American Airlines has chosen to keep its fleet of Boeing 737 MAX grounded until at least August 19, even if it means canceling 115 flights a day in summer season, as probes into the troubled jet continue and new sales have frozen. The 737 MAX 8 airliners were grounded worldwide after a fatal crash of an Ethiopian Airlines flight, which killed 157 people on board. The grounding has already resulted in the cancelation of about 90 flights per day through early June, and the extension may put a strain on American’s ability to meet demand for seats during upcoming peak travel season.