Most large airports will definitely have primary radar covering the terminal control area, but the range of these is typically only some 60nm. Primary radar re

Most large airports will definitely have primary radar covering the terminal control area, but the range of these is typically only some 60nm. Primary radar requires relatively a lot of power, and has other issues (e.g. target correlation) that make it of limited use for ATC purposes during enroute flight. If such radars exist, for military purposes for example, ATC may not have access to them as it's not really essential for their work. There are also large coverage gaps over oceans and in remote areas where nobody cares to monitor. These radars would only have a range of a couple hundred nm maximum, so they would not see deep into the Indian Ocean either. So called 'over the horizon' radars also exist, but require truly massive amounts of power, not to mention capital to build, and also have very low spatial resolution. Apparently Australia's $1.8bn system was aimed in the wrong direction at the time of MH370's disappearance, or it might have had some low precision data to contribute.