Surveillance aircraft usually operate at high altitudes. The Russian Tupelovs I mentioned flew very high just outside our borders and could look down some tens of miles into the interior of our East Coast, monitoring telecommunications. The Air Force watched them but didn't interfere.
Surveillance using satellites is de-facto accepted international practice. Planes, violating other country's airspace is another matter. Tupolevs flew just outside of the borders. U2s were flying inside Soviet borders at extremely high altitudes until the Soviets started shooting them down in 60-s. Neither USA nor Russia/USSR would accept foreign planes flying over their territory without permission. Iran suppose to have the same rights.