(Reuters) - Boeing Co delivered 38% fewer planes in the first seven months of 2019 than the same period a year earlier, as the grounding and doubts around the future of its best-selling 737 MAX jets hurt operations.

FILE PHOTO: A worker walks past unpainted Boeing 737 MAX aircraft seen parked in an aerial photo at Renton Municipal Airport near the Boeing Renton facility in Renton, Washington, U.S. July 1, 2019. REUTERS/Lindsey Wasson

Deliveries totaled 258 aircraft in the seven months through July, compared to 417 last year, and trailing far behind the 458 aircraft handed over in the same period by European rival Airbus SE.

The numbers put Boeing on course to lose the crown of world’s biggest planemaker, which it has held uninterrupted for seven years.

The 737 MAX has been grounded worldwide following two fatal accidents that killed more than 300 people and both Boeing and airlines continue to extend the timelines for when it will return to service.

Last month, the company posted its largest-ever quarterly loss due to the spiraling cost of resolving issues with the MAX, warning it may have to halt production of the grounded jet altogether if regulators around the world do not give clearance for it to fly again soon.

A new problem identified with the MAX in June has delayed the aircraft’s entry into service until at least the end of September, disrupting schedules for airline operators, who have demanded compensation from Boeing for their loss.

One major client, Southwest, has already removed the MAX from its schedules until early January.

The U.S. planemaker is still ahead of Airbus on combined deliveries of its widebody jets, the 777 and 787 Dreamliner, which stood at 24 and 90, respectively, through the first seven months of 2019, compared with 25 and 80, a year earlier.

Airbus delivered 60 of its widebody A350 jets, up from 46 planes, a year earlier. Deliveries of Airbus’s widebody A330 aircraft were 24 planes through July this year.

Both Boeing and Airbus have seen deliveries of their four-engine jumbo jets shrink in recent years as airlines prefer modern fuel efficient twin-engine passenger jets.

Boeing said deliveries of its iconic 747 four-engine jets were flat at four, behind its European competitor the A380 manufactured by Airbus, which saw deliveries of the superjumbo fall to five, from seven last year.

Boeing’s net order after cancellations were a negative 88 aircraft so far in 2019, trailing the 79 aircraft orders won by Airbus.