Hi, KMD this is CW,
With the proper selection of QRG (band) HF would be VERY RELIABLE even with high QRN and the poor current HF antennas.
I NEVEER lost a QSO in several thousands hours of HF operation using 200 W out sometimes lowering to 1.8 MHz (phone) due severe QSB.
In just one case due a VERY STRONG WX System i faced almost complete blackout of powerful MW BCST STN 80nm from my PSN but this is RARE.
I don´t believe, based in ACARS msg´s, they tried to use comm, HF or other.
They should be looking to other priorities.
The info on QRN at the night i think was lost and i think was not a factor.
On good antennas look at the trailing wire (30,000 ft) used by the 707 of USN for VLF to subs.
Unfortunately the current HF antennas are VERY POOR.