The words fairing, faring sound the same but have different meanings and spellings. Why do fairing, faring sound the same even though they are completely different words?
The answer is simple: fairing, faring are homophones of the English language.
An auxiliary structure or the external surface of a vehicle, such as an aircraft, that serves to reduce drag.
Chiefly British A gift, especially one bought or given at a fair.
Present participle of fare.
An adventure, trek, journey.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").