Barely 24 hours after the unions representing flight attendants at American, Southwest, and United Airlines called for the Boeing 737 MAX to be grounded, and as the United States became the last country on the planet still allowing the plane to fly in its airspace, President Trump acted.

He overruled his Transportation Secretary and the Federal Aviation Administration Wednesday, ordering the planes out of the skies.  

Any 737 MAX airplanes that were currently in the air at the time of the announcement Wednesday afternoon, "will be grounded upon landing at the destination," Trump said.

"Boeing is an incredible company," Trump continued, as quoted by The Washington Post. "They are working very very hard right now, and hopefully they'll very quickly come up with the answer, but until they do, the planes are grounded."

The controversy arose after two new Boeing 737 MAX 8s crashed in the last five months: an Ethiopian Airlines flight that crashed on Sunday with all 157 people aboard lost, and a Lion Air flight out of Indonesia that crashed in October, taking the lives of 189.

Meanwhile on Wednesday, the FAA issued a statement saying that it was grounding the airplane--barely 18 hours after insisting that it wouldn't do so, and after Transportation Secretary Elaine Chao and her staff actually flew on a 737 MAX--based on new information:

The FAA is ordering the temporary grounding of Boeing 737 MAX aircraft operated by U.S. airlines or in U.S. territory. The agency made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today.

This evidence, together with newly refined satellite data available to FAA this morning, led to this decision. The grounding will remain in effect pending further investigation, including examination of information from the aircraft's flight data recorders and cockpit voice recorders. An FAA team is in Ethiopia assisting the NTSB as parties to the investigation of the Flight 302 accident. The agency will continue to investigate.

The president's decision here has the unusual distinction of being both surprising and perhaps unavoidable. 

Surprising, because for President Trump, whose foreign policy is literally called "America First," it has to go against the grain to overrule his own cabinet, and then fall in line behind more than 30 other countries including China, Indonesia, Canada -- and the European Union. 

Besides, Boeing, the airlines themselves, and the pilots' unions, as my colleague Chris Matyszczyk pointed out, all had said they believed the 737 MAX should stay in the air. 

It's interesting also here that the pilots and flight attendants seem to have diverged. But in the end we have a situation in which defenders of continuing to the fly the plane found themselves forced to prove a negative.

As the airline site One Mile at a Time put it, U.S. fight attendants and the aviation administrations in other countries weren't grounding the 737 MAX because they knew it was safe. They were doing so because they weren't 100 percent sure it wasn't unsafe.

That's why probably, in the end, this decision also turned out to be inevitable.

The flight attendants unions have compiled a string of wins lately, managing to get some provisions they'd wanted for years tucked into the aviation bill Trump signed last year, and then getting far out in front of the public reaction to the partial government shutdown -- with the head of United's flight attendant union being called "the most powerful flight attendant" in America as a result.

Same thing here, really: While the pilots were apparently content to continue flying (despite accounts that several pilots had in fact reported some safety concerns about the 737 MAX), the passengers and flight attendants were far less willing.

Southwest at least was already offering to waive change fees for customers who were afraid of flying on the 737 MAX.

The practical effects? Southwest has 750 Boeing 737s, and the latest numbers I found show that 34 of them are the 737 MAX version, flying a total of about 160 flights each day.

American has 24, doing about 90 total flights every day. United has 14 of the slightly larger later variant, the MAX 9, doing 40 routes per day.

Those planes are now grounded, and while it's not a crippling number of routes, it is disurptive. The airlines will have to either cut some routes, or find ways to cover using other airplanes temporarily.

And that's the key word here, we hope: temporarily.

Flying commercially is safer than it's ever been, and far more safe than most other modes of travel, stastically speaking. I'm sure everyone hopes and prays that officials can figure out what if anything was wrong, fix it, and get the planes back in the air, safely carrying passengers, as soon as possible.