Are you starting to realize that becoming 'fluent' in the NATO phonetic alphabet is more challenging than simply matching 26 letters to 26 words ought to be? Do some letters occasionally just come up blank in your heads? Can't remember if it's 'india' or 'indigo', 'whiskey' or 'whisker', 'bravo' or 'beta'? Does your brain insist that U is 'unicorn', not 'uniform'?
It just takes some practice, and that's exactly what this tool is designed to help you with.
This tool presents you with randomly-generated codes that follow a variety of real-world specifications (US aircraft registration, US amateur radio, etc.). See it, take your best guess at saying it out loud, then hit the "Reveal" button to see if you were right. Hit the "Next" button to repeat the process forever.