Any plane moving above 500kmph will create enough shock-waves to be detected by both MWIR and LWIR QWIP/QDIP sensors. These modern IR sensors are much more advance than their predecessors. Also, it's literally impossible to completely eliminate skin friction and heating of surrounding air as a consequence.
Both radar and IR sensors are important and are here to stay even in 6th or 7th gen aerial warfare, IMO.
Both radar and IR sensors are important and are here to stay even in 6th or 7th gen aerial warfare, IMO.