• The US joined Europe and others in grounding all Boeing 737 Max airplanes on Wednesday.
  • Around the world, hundreds of flights have been canceled after the plane was involved in a deadly crash on Sunday in Ethiopia.
  • Southwest, American, and United operate the plane in the US.

President Donald Trump announced on Wednesday that the US would join Europe and many countries outside the continent in grounding all Boeing 737 Max airplanes after the model was involved in a deadly crash for the second time on Sunday.

At the time of Trump’s announcement, dozens of the planes – operated by American, Southwest, and United – were still airborne. The Federal Aviation Administration confirmed that it was ordering the temporary grounding of Boeing 737 Max aircraft “operated by US airlines or in US territory.”

American Airlines said in a statement to Business Insider that it had 24 aircraft affected by the directive and was “working to rebook customers as quickly as possible.”

At least six American flights were canceled between New York's LaGuardia Airport and Miami. It's possible that red-eye cross-country flights on Wednesday evening could be affected.

Southwest Airlines, which earlier on Wednesday had said it had waived flight-change fees and was working with passengers who wanted to avoid flying on the aircraft in question, said it was "seeking confirmation and additional guidance from the FAA."

Southwest has the largest number of the aircraft, with 34 of the planes.

United Airlines, which operates 14 737 Max 9s, said the plane is used on about 40 flights a day, but it was finding alternative aircraft to serve those routes.

"We do not anticipate a significant operational impact as a result of this order," the company said in a statement. "We will continue to work with our customers to help minimize any disruption to their travel."

Boeing CEO Dennis Muilenburg said in a statement that the company had consulted federal authorities and recommended the temporary restriction to the FAA "out of an abundance of caution."

"We are supporting this proactive step out of an abundance of caution," the statement said. "Safety is a core value at Boeing for as long as we have been building airplanes; and it always will be. There is no greater priority for our company and our industry. We are doing everything we can to understand the cause of the accidents in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again."

More on Boeing's 737 Max 8 and the Ethiopian Airlines disaster: