The grounding of Boeing 737 Max jets likely means that fare increases this summer will be larger than already expected and airlines will struggle to handle disruptions such as storms that shut down hub airports.
With Max jets grounded after two deadly accidents, U.S. airlines will operate about 200 fewer daily flights than planned through the heart of the peak summer season. That's around 35,000 seats lost every day.
Travel-data firm Hopper said this week that it expects the average domestic round trip in May will cost $236, 7% more than a year ago, and keep rising in June. Most of that increase is due to the price of jet fuel and other economic causes, but some of it is due to the Max, according to Hayley Berg, the firm's economist.
The grounding of Max jets will leave other planes more crowded.
"We expect a certain level of chaos," said Henrik Zillmer, CEO of AirHelp, which helps travelers get compensation for travel disruptions. "With so many passengers being rebooked, flights may get more overbooked than usual, especially when weather or other factors cause cancellations."
For some passengers, the grounding of the Max will mean a change in travel plans.
Southwest, American and United are the three U.S. airlines that used the Max before regulators grounded the jet in mid-March. They are taking passengers whose original itinerary included a Max and rebooking them on flights using other planes.
That could mean a nonstop flight turns into a connecting flight. Or it might arrive several hours later than the traveler expected.
Travelers who don't like their new itinerary have limited options. Zillmer said under most international laws the grounding of the Max by governments is considered an extraordinary circumstance, and passengers aren't eligible for compensation for resulting disruptions.
Travelers can seek a full refund, however, even if they bought a nonrefundable ticket.
"If the new flight doesn't work for you, you might consider getting your money back and finding a flight that suits you on your own," said Tracy Stewart, content editor for travel site airfarewatchdog.com. But he warned that you might end up paying more that way, especially because prices tend to rise closer to summer.
Southwest Airlines has more Max jets than anyone else—34—and was scheduled to receive another 41 later this year, although that schedule is now in doubt.
Still, the Max accounts for only about 5% of the Southwest fleet and less than 1% of the passenger-carrying capacity of U.S. airlines overall.
Berg, the Hopper economist, said heavily traveled routes will probably see little disruption, but routes with lower demand might see some cancellations or suspensions for a short time.
One example is Pittsburgh, where Southwest plans to suspend service to Los Angeles and Cancun, Mexico, next month because of the Max situation.
Until the Federal Aviation Administration grounded the Max in March, Southwest was using them on many trans-continental flights. American Airlines, with 24 Max planes, flew them heavily in and out of Miami.
Southwest and American both say have redistributed their fleets so that no routes suffer a disproportionate seat shortage due to the grounding of the Max.
"The Max impact is not isolated to any region or route," said Southwest spokesman Chris Mainz. "On any given day, with 34 Max, we could have 146 flights on 115 routes touching 44 airports with a Max. And we don't schedule them the same every day. The impact truly is across our network."
United hopes to have its Max jets flying again in July, while Southwest and American have dropped them from their schedules into August. Boeing is working on a software fix that it hopes will convince regulators to let the planes return to service.
It remains to be seen how many travelers will be reluctant to board the plane after crashes that killed 346 people in Indonesia and Ethiopia. Preliminary reports found that software on the plane forced the noses down, and pilots were unable to regain control.
If the planes are cleared to fly, passengers who cancel a reservation or refuse to board the plane because they are afraid won't be eligible for compensation, according to AirHelp's Zillmer. They can ask the airline for a refund, but that might not work either.
"By the time fall rolls around and the software updates have been applied and Maxes are back in operation, it's pretty unlikely airlines would be as flexible with refunds and ticket changes," said airfarewatchdog's Stewart.
It will be up to consumers, he said, to check what kind of plane the airline plans to use before they click "buy" on the ticket.