The extended grounding of Boeing Co.’s 737 Max planes forced Ryanair Holdings to scale back growth plans for next summer, putting the airline industry on notice that the crisis is starting to affect longer-term plans.

With a return date for the Max still uncertain after two fatal crashes, Ryanair is likely to receive barely half of the 58 planes it was expecting for the 2020 peak schedule, the Irish company said Tuesday, estimating that the reduction will wipe 5 million passengers from its full-year tally.

“Boeing is hoping that a certification package will be submitted to regulators by September with a return to service shortly thereafter,” Ryanair Chief Executive Michael O’Leary said in a statement. “We believe it would be prudent to plan for that date to slip by some months, possibly as late as December.”

Ryanair’s announcement shows how a further extension to the Max grounding would have significant fallout for airlines, which draw up schedules about six months in advance. Air travel is particularly weighted toward the summer season in Europe, with passenger numbers typically surging from the Easter holiday, which starts April 10 next year.


Although U.S. operators of the Max haven’t yet talked about changing their growth plans beyond this year or readjusted deliveries, it will probably take 15 to 18 months for the carriers to catch up to their original schedules, said Savanthi Syth, a Raymond James Financial Inc. analyst.

The timing depends on Boeing resuming its original delivery schedule, after slowing Max production rates to 42 from 57 aircraft a month, Syth said.

Carriers will probably limit the expansion of the seat supply until late next year, said Helane Becker, an analyst at Cowen & Co. “We think capacity growth will remain muted until the end of 2020 so that the first ‘normal’ year for capacity growth will be 2021,” she said.

Ryanair, Europe’s biggest discount airline, faces a particular issue because it has ordered the high-capacity Max 200 version of the 737, which requires separate certification from U.S. and European regulators. Approval for flights could take up to two months beyond the baseline model’s return to service, it said.


Other Max customers are already beginning to look at fleet moves for next year in case the grounding drags on. TUI, the world’s biggest travel company, wants the model to replace existing 737s and at some point will need to decide whether to keep the older aircraft in service, a spokesman said.

Norwegian Air Shuttle has the greatest current exposure in Europe to the Max crisis, with 18 planes grounded, but agreed in April to postpone the handover of 14 more due in 2020 and 2021 and keep older planes for longer as it reins in capacity as part of a plan to resolve a debt crisis.

FlyDubai, which has idled 14 Max planes that have been delivered out of 251 ordered, according to Boeing, said last week that the continued grounding had forced it to delay the Oct. 1 launch of flights to Budapest, adding that passengers could switch to sister company Emirates. Emirates President Tim Clark himself predicted in June that the model wouldn’t return to the skies until next year because of the need for national and regional regulators to agree on a common position.

In the U.S., American Airlines Group Inc. and United Airlines Holdings Inc. last week pulled the narrow-body off their schedules through early November, in the latest sign the jet may not resume commercial service this year. Southwest Airlines Co., the largest operator, has taken the Max out of its schedules at least through Oct. 1.


O’Leary, who warned last week that Ryanair might need to pare growth plans in light of the Max crisis, said his company can take delivery of only six to eight new aircraft a month, and is now planning to have 30 incremental aircraft for next summer.

That will cut the growth rate to 3% from 7%, necessitating some base cuts and closures for both the coming winter schedule and the 2020 peak, the airline warned, with discussions with airports and unions set to determine which of its poorer-performing operations will go.

Ryanair said it will work with Boeing and the European Aviation Safety Agency to recover the delivery delays during the winter of 2020 in order to restore growth to “normal levels” in summer 2021.

Aviation regulators grounded the newest 737 after two crashes killed 346 people. On June 26, the Federal Aviation Administration disclosed a separate software glitch it had found during simulator testing.


That issue requires additional work by Boeing and is further delaying the Max’s return to service.