It wasn’t just VHF and UHF airbands that enthusiasts listened to during the 1950’s and 1960’s but also the HF Aeronautical bands
This Nova-Tech advert from Flying Magazine December 1961 says their 4 band aircraft radio ‘Receives L.F. aircraft transmissions on 3023.5’
This Model 102 (Actually a Perdio Multiband 102) was advertised in 1964 as having Short Wave which received the Aeronautical band
Frequency guides were not available in the 1960’s instead enthusiasts used RAF and USAF En-Route supplements. These are the HF frequencies published in the January 1965 United Kingdom RAF En-Route
U.S. Military Air Transport Service (MATS)
USAF Croughton Air-Ground Station was listed in USAF and RAF En-Route Supplements
In the RAF En-Route United Kingdom Oct 1959 edition it listed the following: Croughton Airways – 6730.5 (Weather Information), 13215.5
For a personal retrospective view please check out Colin McKeeman’s post here – https://swling.com/blog/2017/02/guest-post-colins-retrospective-on-monitoring-aeronautical-communications and Colin’s historical aeronautical HF logs https://banterops-aerohflog.blogspot.com/
Colin has also produced an excellent book called ‘A History Of The Birdlip Aeronautical Communication Complex 1940 – 2015’. You can order it directly from Colin by sending an email to downrange@eircom.net – The book costs £30 (including P&P to U.K. mainland addresses)
These articles from a US magazine called ‘Popular Electronics’ provide details on monitoring aircrafts on HF in the 1950’s