(CNN) Passengers do not have many options if they are booked on flights in the United States and learn that they will be on the same model of aircraft, the 737 MAX 8, that crashed in Ethiopia over the weekend. While passengers can always choose not to get on a plane if they feel unsafe, the two major US airlines that have 737 MAX 8 planes are not grounding those aircraft or changing their standard flight cancellation, change or refund policies.

An Ethiopian Airlines flight from Addis Ababa to Nairobi, Kenya, crashed Sunday morning, killing all 157 people on board, according to the airline. The flight was on a 737 MAX 8 plane made by Boeing, an American company. This is the second fatal crash of a 737 MAX 8 in the past six months.

After Sunday's crash, passengers booked on Southwest and American airlines, both US-based companies that fly the Boeing model, began asking questions on Twitter about the safety of their upcoming flights.

Southwest spokesperson Brian Parrish said they were "fielding some questions" from customers asking if they were booked on 737 MAX 8 aircraft. He said they were responding to customers individually and that they "remain confident in the safety and airworthiness of our fleet of more than 750 Boeing aircraft."

American Airlines said it continues "to collaborate with the FAA and other regulatory authorities" and that they "have full confidence in the aircraft and our crew members, who are the best and most experienced in the industry."

@SouthwestAir are you planning on grounding the supermax?#Boeing — Phil Angel (@philangel72) March 11, 2019

@SouthwestAir can you publish a list of routes for the 737 max so I can avoid them? — Chris Coffee (@ChrisCoffee1126) March 11, 2019

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