At a guess: AirTags (and all Apple devices) get their location from nearby iPhones. If nearby passengers turn on Airplane Mode before departure, their phones stick to being located at the departure airport. When they land and turn off Airplane mode, there’s a short window where they broadcast their “current” location (the departure airport) before getting a new GPS signal. That’s what your M1 is picking up when you land.

Ah, cool. I had thought it was just paired with my phone, and was somehow sad that it could not see it for a while. Your explanation makes more sense.

Whenever I get on the subway, right after I exit the train I get a notification that my MacBook's left behind at the train station I boarded at. That makes sense then

I get notifications that my AirPods are 'left behind' at the gym when I'm driving home, even though... I'm wearing them in the car and the case is in my pocket.

Yet... the one time I actually forgot the case in my gym locker, and got to the car... nothing.

Happens sometimes when I leave the office too; half a mile from the office I get an alert that I've left my AirPods at the office even though - again - I'm wearing them, they're connected to the phone I'm holding which is also with me (and moving) and the case is with me too.

This will become a 'boy who cried wolf' situation soon, if it's not already there.

So many red flags there. Wearing airpods while driving, and then also holding your phone while driving?

People like you make me nervous when I drive.

The pros have transparent mode, so wearing them in that mode is not an issue.

"they're connected to the phone that is in my shirt pocket".

Does that make you feel safer?

Guess what? It also exhibits the exact same behavior even when I'm a passenger (not driving) in the exact same circumstances.

This happens to me on car rides as well. I’ve made my friends pull over so I could check that I indeed packed the backpack with my AirPods.

I have that happen just by leaving my MBP in the trailer I'm towing behind me. Periodically it tells me I left it somewhere along the road.

Just speculating, but if the last Find My ping of the laptop happened at the origin airport, and you're disabling airplane mode on your phone at the destination, the Find My network could well believe your laptop is still at the origin airport until the laptop pings again.