Yep, an issue with 'old fashioned' comms.
But modern comms will switch bands or 'glide' frequencies in sympathy with the changing ['fading'] MUF, etc. and can do so automatically (using OWF in conjunction with IPS also helps). Combine that with modern encoding/digital modulation and say DRM of the right kind—Digital Radio Mondiale—for audio etc. and it's pretty damn reliable.
Want better? Diversity TX/RX and or multichannel via in-band and or cross-band into comparators etc.
...for varying definitions of 'reliable' :)