I’m not sure that the fighters would be lost during a retreat. I do believe it is perfectly legal to fly fighters 4 spaces into combat, then have them retreat 1 space from where any of the units involved in came from. This is assuming both the fighters and CV entered into the same SZ for combat but from different directions.
Actually, in Spring 42 from what I understand, fighters can retreat to ANY adjacent territory regardless if units came from there or not (anyone know what version of AA this started in?). In theory, you could take the CV off as a hit, retreat the fighters to an adjacent sz and as long as another one of your CVs cold move into that zone during non-combat, the fighters land and all is well.
I believe it a bit unethical, but legally you could plan to have your planes fly 4 spaces into battle, place enough CVs for them to land in that SZ, do combat, lose those CVs but plan on having your fighters retreat to additional CVs in adjacent SZs that would in effect, have the fighters fly 5 spaces.