Southwest Airlines used to tuck the same safety information card into the seat back pockets of its Boeing 737-800s and Boeing 737 Max 8s.The combined safety card system worked – until the Max 8 was grounded earlier this year following two fatal crashes in less than five months that killed 346 people.

After those incidents, passengers who saw Max 8 in bold yellow letters on the safety card bombarded Southwest flight attendants and the airline's social media representatives with questions about whether they were on the troubled plane. As the grounding dragged on, the airline had to repeatedly reassure customers that, no, they weren't on a Max 8.

In mid-May, Southwest quietly introduced separate cards for the two planes. Now the 737-800 is the only plane listed on the safety card for that aircraft.

Southwest spokesman Chris Mainz said the move was made "to alleviate any confusion from customers so they know exactly what aircraft type they are on.''

The new Max safety card won't be used, of course, until the plane is back in service. The timing of the plane's return is unclear. The latest wrinkle: the FAA discovered a new flaw in the plane.

Airlines are already preparing for a new round of traveler questions, concerns and, in some cases, refusals to fly on the plane once the FAA clears the Max 8 to return to service.

Southwest is the largest U.S. operator of the Max, with 34 of the planes in its fleet. American is next, with 24, followed by United, which has 14 Max 9s, a larger version.

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