Two stewardesses look at flowers left in commemoration for the victims of Malaysian Airlines flight MH17 at Schiphol Airport, near Amsterdam, the Netherlands. EPA/ROBIN VAN LONKHUIJSEN

AMSTERDAM — The flight attendants stand out. They come in groups of one and two, sometimes larger, like cabin crews arriving straight from a just-landed plane. They come to place flowers outside Terminal 3 at Schiphol Amsterdam Airport, where Malaysia Airlines flight 17 departed for a final time last Thursday before it was shot down over eastern Ukraine.

The flight attendants are joined by tourists from abroad, the Dutch on their way to a vacation, sometimes even the victims’ families. But these others mostly blend in. The flight staff are unmistakable as they place their single roses and bushels of sunflowers or daisies. The bright blue uniforms of KLM. The dark red jacket of Delta. The tight sea-foam green of Korean Air. The head scarves falling from the red pillbox hats worn by Emirates Airlines.

They all come from different tribes and go their separate ways, but here they are coming together, to mourn and to honor.

Often, these flight attendants seem to linger above the flowers longer than others, sometimes tearing up. They have a particular understanding of the risks of flying, of the responsibilities, of how suddenly it can all go wrong.

When things do go wrong — anywhere in the world’s airspace — flight attendants from every airline appear to run elevated risks of developing post-traumatic stress disorder, The Atlantic’s Rebecca J. Rosen reported on Tuesday. “Two tragedies in such close proximity” — meaning, the loss of two Malaysia Airlines flights this year — “may have compounding effects and lead to even greater rates of PTSD,” she wrote.

One afternoon here this week, a flight attendant in a green skirt stood crying by the flowers. Another flight attendant in a blue jacket patted her on the back and spoke to her. They both smiled a little.

It wasn’t clear which airlines they worked for. And in that moment, it didn’t matter.

Todd C. Frankel is a reporter covering people and policy. You can follow him on Twitter: @tcfrankel.