Most planes broadcast their position using ADS-B, and some websites collect these signals and visualize them so you can track flight paths. Somebody broadcast a fake flight path that draws a picture of JD Vance on these sites: https://globe.adsbexchange.com/?icao=adfdf9&lat=26.678&lon=-...
To expand on that, those websites mostly operate on random volunteers self hosting a (starting price) fairly cheap receiver and antenna with an open source stack that feeds the ADS-B data to the website operator in exchange for nothing or free "premium" benefits.
The spoofer could have just sent them fake location information drawing an image using latitude, longitude and altitude for color (in the default view flight paths have different colors based on the altitude of the plane at that point in time).
They could have built an antenna and actually broadcast this data, but that would be a lot more effort and most likely some form of crime.
ADS-B (Automatic Dependent Surveillance-Broadcast) is a protocol for planes to publish their positions, so help with the whole "not crashing into each other" thing. The data is mostly for pilots and air traffic control, but it is publicly available, and there's a number of sites that track the data so that you can see what planes are overhead or whatever.
Someone spoofed Airforce One's transponder, had it declare itself as "VANCE 1", and then fly a pattern to display the meme. Or lied to one or more of the major sites, pretending to be listening in on the ADS-B signals. It's unclear. Regardless, it's a very funny hack.
It’s basically the modern radar system as in it supplies the data air traffic controllers see on their screens. Civilian ATC doesn’t really use actual radars any more.
That said, TCAS (Traffic Collision Avoidance System) does not operate on flight data reported by ADS-B.
