Why, exactly, did Donald Trump not join Emmanuel Macron, Angela Merkel, and Justin Trudeau at Saturday’s commemoration of the 100th anniversary of the original Armistice Day? I don’t know, and I don’t think anyone outside the White House does at this point.

What I do know is that one hypothesis that has shown up in many stories about his no-show—that Marine One, the presidential helicopter, “can’t fly” in the rain—doesn’t make sense.

As you’re looking for explanations, you can dismiss this one. Helicopters can fly just fine in the rain, and in conditions way worse than prevailed in Paris on November 10.

Eliot Cohen: Trump fails his rendezvous in France

First, about helicopters and weather. (What follows is based on my having held an instrument rating as an airplane pilot for the past 20 years, and having worked in the Carter-era White House and occasionally having been aboard the Marine One of that era.)

There is nothing special about the rain-worthiness of the helicopter any president normally uses. In principle, any helicopter can fly in clouds or rain. The complications would be:

Icing: This is one of the big weather-related perils of flying. (The other is thunderstorms.) If (a) an aircraft is inside the clouds, and (b) the temperature is at freezing or below (down to about -15 or -20 degrees Centigrade, when it becomes so cold that the water behaves differently), there’s a risk of icing: ice piling up on the wings, control surfaces, etc. This changes the shape of the airfoils, and it essentially makes a plane unable to fly. This was part of the story of the commuter plane that crashed going into Buffalo a few years ago. I did a long illustrated post about what icing looks like, and how it kills, back in 2011. Other posts are here and here.