The Federal Aviation Administration issued an emergency order Wednesday grounding all Boeing 737 Max aircraft in the wake of a crash of an Ethiopian airliner that killed 157 people, a reversal for the U.S. after federal aviation regulators had maintained it had no data to show the jets are unsafe.    The decision came hours after Canada joined some 40 other countries in barring the Max 8 from its airspace, saying satellite tracking data showed possible but unproven similarities between the Ethiopian Airlines crash and a previous crash involving the model five months ago. The U.S., one of the last holdouts, also grounded a larger version of the plane, the Max 9.    Daniel Elwell, acting head of the FAA, said enhanced satellite images and new evidence gathered at the crash site led his agency to ground the jets.    The data, he said, linked the behavior and flight path of Ethiopian Airline's Max 8 to data from the crash of a Lion Air jet that plunged into the Java Sea and killed 187 people in October.    "Evidence we found on the ground made it even more likely that the flight path was very close to Lion Air's," Elwell told reporters on a conference call Wednesday.    Elwell said he couldn't detail what was found on the ground because the investigation is in its early stages and is continuing.    The Ethiopian plane's flight data and voice recorders will be sent to France for analysis, Elwell said. Some aviation experts have warned that finding answers in the crash could take months.    President Donald Trump, who announced the grounding and had received assurances Monday from Boeing CEO Dennis Muilenburg that the Max aircraft was sound, said the safety of the American people is of "paramount concern."    Trump said any plane currently in the air will go to its destination and then be grounded, adding that pilots and airlines have been notified.    Boeing issued a statement saying it supported the FAA's decision even though it "continues to have full confidence in the safety of the 737 MAX." The company also said it had itself recommended the suspension of the Max fleet after consultations with the FAA and the National Transportation Safety Board.    "We are supporting this proactive step out of an abundance of caution," Boeing said.    The groundings will have a far-reaching financial impact on Boeing, at least in the short term, said John Cox, a veteran pilot and CEO of Safety Operating Systems.    In addition to those that have already been grounded, there are more than 4,600 Boeing 737 Max 8 planes on backlog that have not yet been delivered to airlines.    "There are delivery dates that aren't being met, there's usage of the aircraft that's not being met and all the supply chain things that Boeing so carefully crafted," Cox said. "If they can't deliver the airplanes, where do they put the extra engines and the extra fuselage and the extra electrical components?    "All of those things are going to continue to show up, but they're not going to be able to deliver the airplanes, so it has a very far-reaching effect to many, many different organizations."    Even so, Cox thinks Boeing will recover because the planes typically fly for 30 to 40 years and any needed fix will be made quickly, he said. Officials with the city of San Antonio Aviation Department said the impact of the grounding hasn't been felt yet at San Antonio International Airport because not many of the affected jets fly in and out of the airport. But some passengers who arrived from other states said they have experienced some delays. Tim Manzella, who flew into town Thursday, said he and his wife were a little bit uneasy about flying since his native country of Germany had already banned the jets. "It makes me nervous because I am afraid of flying anyway, so I definitely spent last night checking if our flight was affected, but we were lucky. I think the model they used on our particular flight is a previous model that is supposed to be safe," he said. William Washington, who flew with his band into San Antonio, said he welcomed the grounding decision. "The thing about airlines is that they plan for these things so much in advance that one wrong issue affects everybody. If late means saving your life, be late," he said. There are a few ways to know if you're booked on a 737 Max 8 or Max 9 jet. You can check your airline's website or app. The flight number will indicate what type of airplane is assigned to the flight. Check the registration number of the airplane on the FAA website. The number is clearly marked on the side of the plane.