|Royal Canadian Air Force ensign (wikipedia)|
Commercial aircraft use ADS-B transponders to identify their location to other aircraft to avoid collisions; you can read up on the technology and history here. Military aircraft, from my understanding, have ADS-B transponders, but do not use them when they are operational, since it would give away their location. Additionally, some planes seem to use some features of the transponder, but not others; so you could have a plane that is beaconing coordinates, but not altitude, for example. This is an effort to obfuscate the information from evil-do'ers. When a plane isn't transmitting its coordinates, MLAT (essentially triangulation) is used to estimate the plane's location if enough amateur radio receivers can pick up the signal of the plane. The likelihood of that increases as the plane increases its altitude, since it can "see" more of the earth's surface from higher altitudes (the earth is round, eh).
But how do you, sitting at home, watch these planes' transponder signals? There are several commercial providers, businesses, that for a small monthly fee, will allow you to track commercial, and some military, planes. FightRadar24.com, PlaneFinder.net, and surely many others. I have used them, and I do use them, but they have a small problem. They're commercial businesses, and the militaries of the world are pretty smart; they have asked these businesses, to avoid any trouble, to NOT display their aircraft. To censor their feeds, so people can't see military aircraft flying over their houses. The military does so under the guise of Operational Security, OPSEC. I respect the idea of OPSEC, but in this case it's likely not the reason to deny the public this information, since they are emitting the signal to begin with. If the issue was truly OPSEC, they would turn the transponder completely off, as they actually do when they are conducting operations in a war-zone. The military doesn't want you asking questions about their air movements, and censoring the data commercially available, that they are blatantly broadcasting for anyone to hear with the right equipment, ensures you don't know what they're doing, and ensures you can't stay informed.
Except... There is a crowd-sourced web site, which isn't a commercial enterprise, called ADSBExchange.com. They run on a shoestring budget, and the reporting servers are down sometimes, but overall the system works. The following links will show you reports of the Royal Canadian Air Force's planes that have been caught by people triangulating, or receiving, ADS-B signals from Canadian military planes, worldwide.
It seems these queries will only work when the system isn't under a lot of load. I find that early in the morning I have a better chance for these reports to work.