Yup, ATC error can cause this sort of thing (super busy and new or just spaced out something), so can pilot not heeding an ATC voiced command for maintaining a specific alt/speed/direction. Each plane is directed to a heading altitude n speed depending on those things, some planes are faster than others ATC a very stressful job because you have to be on watch and make quick calls whenever something changes (weather , new craft clocks into your airspace and emergencies included) None of that means anything if the pilot suddenly passed out without warning though, all the radar peeps would see was the blip going off course and they would radio in telling them to correct course and if no response they would do the same for any other plane they may get close to and use special call signs that let everyone know something is wrong. and so on and so on. Since one plane was landing, if it was the actual airstrip then the Tower would of been directing them (eyes on) Why da hell another small plane was allowed to be in that airspace at that time is a big WTF though. Was it taking off? was it crossing the airspace? were the two planes dogfighting? srsly.

Yup, ATC error can cause this sort of thing (super busy and new or just spaced out something), so can pilot not heeding an ATC voiced command for maintaining a specific alt/speed/direction. Each plane is directed to a heading altitude n speed depending on those things, some planes are faster than others ATC a very stressful job because you have to be on watch and make quick calls whenever something changes (weather , new craft clocks into your airspace and emergencies included) None of that means anything if the pilot suddenly passed out without warning though, all the radar peeps would see was the blip going off course and they would radio in telling them to correct course and if no response they would do the same for any other plane they may get close to and use special call signs that let everyone know something is wrong. and so on and so on.