U.S. carriers moved swiftly to comply with federal orders grounding their Boeing Co. 737 Max aircraft and shift passengers to other flights.

Nationwide, the inconvenience for travelers will be muted because the Max makes up about 3 percent of the mainline fleets for three U.S. carriers: American Airlines Group Inc., Southwest Airlines Co. and United Continental Holdings Inc. The Federal Aviation Administration ordered the airlines to stop flying the planes Wednesday after new evidence surfaced in the second fatal crash of the model in five months.

One place that will see more disruption: Miami, where American has concentrated its initial Max deliveries for service to the Caribbean and to New York’s LaGuardia airport.

All together, the three airlines fly 72 of the Boeing 737 Max planes, out of 2,474 jets in their mainline fleets.

American makes about 85 daily flights with the 24 Max jets in its stable of more than 950 planes. Nine Max 8s were in the air when the grounding was announced and continued to their planned destination, the airline said.

“Our teams will be working to rebook customers as quickly as possible,” the carrier said in a statement. American will continue working with federal regulators, the National Transportation Safety Board, Boeing and engine manufacturers, it said.

Nineteen American departures from Miami were expected to be canceled Wednesday, according to Miami aviation officials. Several foreign-based airlines also fly Max aircraft into the city, said Jack Varela, an airport spokesman.

Southwest, the biggest U.S. operator of the jet, has 34 Max 8 aircraft among its more than 750 planes. Most of its fleet consists of the older 737-700 model. Max 8 planes make an average 150 daily trips, or about 4 percent of total flights.

“Southwest Airlines is immediately complying with today’s FAA requirement,” Southwest said in a statement. Southwest said it will use other aircraft in its fleet to meet demand during spring travel, and will offer flexible policies to help customers rebook travel.

United said the grounding would affect about 40 daily flights. The airline will rebook passengers and use spare aircraft to make up for their absence, a spokesman said by telephone. The Chicago-based airline flies only 14 of the larger Max 9 version, which has not been involved in any crashes.

The three airlines, along with their pilots’ unions, said earlier that they remained confident in the safety of the Max. Labor groups representing flight attendants at United and American had called for the planes to be grounded out of an abundance of caution.

All 157 people aboard the Ethiopian Airlines 737 Max 8 died when it plunged into the ground at high speed about six minutes after takeoff near Addis Ababa. Investigators have released no information about what caused the crash. A Lion Air Max 8 crashed off the coast of Indonesia in October, killing all 189 people aboard, following a malfunction of a software feature on the plane that repeatedly forced it into a dive.