MANPADs are only effective at very low altitudes (AGL), fundamentally due to the inability to put much propulsion on a rocket intended to be carried by hand. Su-27s, Su-34s, and Su-35s should fly significantly higher than this altitude during strike and interdiction missions, but doing so exposes them to radar-guided SAM systems like the aforementioned Buk (SA-11 / SA-17) or S-300 (SA-10 / SA-12 / SA-20).