A spell checking system includes a letter spelling engine. The letter spelling engine is configured to select a plurality of candidate letter target strings that closely match a misspelled source string. The spell checking system includes a phoneme spelling engine. The phoneme spelling engine is configured to select a plurality of candidate phoneme target strings that closely match the misspelled source string. A ranker module is configured to combine the candidate letter target strings and the candidate phoneme target strings into a combined list of candidate target strings. The ranker module is also configured to rank the list of candidate target strings to provide a list of best candidate target strings for the misspelled source string.