There were scores of syndicated five minute radio things back then done. They'd be pretaped in bulk for mass distribution to stations on reels or discs to be aired at their own discretion. None of these things would ever air at fixed designated times and were often the kind of "filler"...
Interestingly Zanuck at first wanted Eisenhower to play himself in "Longest Day" for the one scene Eisenhower is in the script but they determined that it just wasn't possible to make him look credible as a 20 years younger version of himself so they instead cast a lookalike in the part, Henry...