However the atmosphere attenuates infrared waves, like bad weather conditions do. In comparison to a radar, it has a limited range. Therefore, the accuracy of IRST systems is better on close range, unlike on radar, the reason for that is the shorter wavelength of Infrared.
Infrared sensors versus Stealth Edit
It is claimed that Infrared seekers can track stealthy targets much better than a radar can do, the reason for that is that stealth aircraft can theoretically be tracked because of their engine emissions, which are usually very hot, especially if the afterburner is used.
However it is possible to hide an aircraft against IR-seekers, using a special ceramic-matrix RAM painting, that is utilized on the engine exhaust nozzles to reduce radar and IR signatures,  but it is also possible to reduce IR-emissions with special engines to cool the exhaust plumes down to temperatures at which their infrared emissions are quickly absorbed by atmospheric carbon dioxide and water vapour.