There are 420 fifteen-letter words containing A and F, https://www.bestwordlist.com/c/a/2/15letterwordswithaf.htm
ABSORBEFACIENTS AFFECTABILITIES AFFECTIVENESSES AFFORDABILITIES
AFFRANCHISEMENT AFTERSENSATIONS AFTERTREATMENTS AMMONIFICATIONS
ANFRACTUOSITIES ANTIFASHIONABLE ANTIFEDERALISTS ANTIFERROMAGNET
ANTIFILIBUSTERS ANTIFORECLOSURE ANTISHOPLIFTING ARIBOFLAVINOSES
ARIBOFLAVINOSIS ARTIFICIALISING ARTIFICIALITIES ARTIFICIALIZING
AUTOTRANSFORMER AUTOTRANSFUSION BAREFACEDNESSES BEAUTIFICATIONS
BEAUTIFULNESSES CALORIFICATIONS CAPRIFOLIACEOUS CENTRIFUGALISED
CENTRIFUGALISES CENTRIFUGALIZED CENTRIFUGALIZES CENTRIFUGATIONS
CERTIFICATORIES CHANGEFULNESSES CHOLECALCIFEROL CHONDRIFICATION
CIRCUMFERENTIAL CIRCUMFORANEOUS CLASSIFICATIONS COCKNEYFICATION
COCKNIFICATIONS CODIFIABILITIES COLORFASTNESSES COMFORTABLENESS
COMMODIFICATION CONFECTIONARIES CONFESSIONALISM CONFESSIONALIST
CONFESSIONARIES CONFIDENTIALITY CONFIGURATIONAL CONFORMABLENESS
CONFRATERNITIES CONFRONTATIONAL CONFUSABILITIES CORPORIFICATION
COSIGNIFICATIVE COUNTERFACTUALS COUNTERFEISANCE COUNTERFESAUNCE
CRESTFALLENNESS DEACIDIFICATION DECALCIFICATION DECERTIFICATION
DEDIFFERENTIATE DEFAMILIARIZING DEFEASIBILITIES DEFEMINISATIONS
DEFEMINIZATIONS DEFENESTRATIONS DEFIBRILLATIONS DEFLOCCULATIONS
DEFORMABILITIES DEFRAGMENTATION DEMOCRATIFIABLE DEMULSIFICATION
DEMYSTIFICATION DEMYTHIFICATION DENAZIFICATIONS DENITRIFICATION
DENITRIFICATORS DESERTIFICATION DESULFURISATION DESULFURIZATION
DETOXIFICATIONS DEVITRIFICATION DEXFENFLURAMINE DIFFERENTIATING
DIFFERENTIATION DIFFERENTIATORS DIFFRACTIVENESS DIFFRACTOMETERS
DIFFRACTOMETRIC DIFFRANGIBILITY DINOFLAGELLATES DISAFFECTEDNESS
DISAFFECTIONATE DISAFFILIATIONS DISAFFIRMATIONS DISAFFORESTMENT
DISCONFIRMATION DISENFRANCHISED DISENFRANCHISES DISFEATUREMENTS
DISFORESTATIONS DISGRACEFULNESS DISINFESTATIONS DISINFLATIONARY
DISINFORMATIONS DISSATISFACTION DISSATISFACTORY DISSYLLABIFYING
DISTASTEFULNESS DIVERSIFICATION DRAUGHTPROOFING EBURNIFICATIONS
EFFECTUALNESSES EFFICACIOUSNESS ELECTRIFICATION EMULSIFICATIONS
ENFRANCHISEMENT ESTERIFICATIONS ETHERIFICATIONS EXEMPLIFICATION
EXEMPLIFICATIVE EXTENSIFICATION FACETIOUSNESSES FACTORABILITIES
FAITHLESSNESSES FAITHWORTHINESS FAMILIARISATION FAMILIARIZATION
FANATICALNESSES FANATICISATIONS FANATICIZATIONS FANTASTICALNESS
FANTASTICATIONS FARTHINGSWORTHS FASHIONABLENESS FATHEADEDNESSES
FATIGABLENESSES FAULTLESSNESSES FAVORABLENESSES FEATHERBEDDINGS
FEATHERSTITCHED FEATHERSTITCHES FEATURELESSNESS FEDERALISATIONS
FEDERALIZATIONS FERRIMAGNETISMS FERROMAGNETISMS FERROMANGANESES
FERROPRUSSIATES FETISHISTICALLY FIBROCARTILAGES FICTIONISATIONS
FICTIONIZATIONS FIDEICOMMISSARY FILTERABILITIES FILTRABLENESSES
FISSIPAROUSNESS FLAGELLOMANIACS FLAVOURDYNAMICS FLEXITARIANISMS
FLIRTATIOUSNESS FLUOROPHOSPHATE FOOLHARDINESSES FORENSICALITIES
FOREORDAINMENTS FOREORDINATIONS FORISFAMILIATED FORISFAMILIATES
FORMALISTICALLY FORMATIVENESSES FORMIDABILITIES FORMULARISATION
FORMULARIZATION FORTUNATENESSES FRACTIONALISING FRACTIONALIZING
FRACTIONISATION FRACTIONIZATION FRACTIOUSNESSES FRAGMENTARINESS
FRANGIBLENESSES FRATERNISATIONS FRATERNIZATIONS FRENCHIFICATION
FRUCTIFICATIONS FUGACIOUSNESSES FUNCTIONALISTIC FUNCTIONALITIES
FUNDAMENTALISMS FUNDAMENTALISTS FUNDAMENTALNESS FUNGISTATICALLY
FURACIOUSNESSES FURFURALDEHYDES FUTILITARIANISM GENTRIFICATIONS
GRANDFATHERLIER GRANITIFICATION HAEMOFLAGELLATE HALFHEARTEDNESS
HALFPENNYWORTHS HEALTHFULNESSES HEMOFLAGELLATES HUMIDIFICATIONS
HYPERFASTIDIOUS HYPERFUNCTIONAL HYPERINFLATIONS IDENTIFICATIONS
INDEFEASIBILITY INDEFINABLENESS INDEMNIFICATION INEFFABLENESSES
INEFFACEABILITY INEFFECTUALNESS INEFFICACIOUSLY INFALLIBILITIES
INFANTILISATION INFANTILIZATION INFEASIBILITIES INFINITESIMALLY
INFLAMMABLENESS INFORMATIONALLY INFORMATISATION INFORMATIVENESS
INFORMATIZATION INFRALAPSARIANS INFRANGIBLENESS INFRASTRUCTURAL
INFRASTRUCTURES INSIGNIFICANCES INSIGNIFICANTLY INSIGNIFICATIVE
INTENSIFICATION INTERFASCICULAR INTERFRATERNITY INTERSTRATIFIED
INTERSTRATIFIES INTRAFASCICULAR IRREFORMABILITY IRREFRAGABILITY
IRREFUTABLENESS JUSTIFIABLENESS KAFFEEKLATSCHES KARSTIFICATIONS
LACTIFEROUSNESS LAPIDIFICATIONS LATENSIFICATION LIGHTFASTNESSES
LIGNOSULFONATES MAGNIFICENTNESS MALCONFORMATION MALFUNCTIONINGS
MANIFESTATIONAL MARGARITIFEROUS MASTERFULNESSES MATERFAMILIASES
MATRIFOCALITIES METAFICTIONISTS METHOXYFLURANES MICROMICROFARAD
MISINFORMATIONS MODIFIABILITIES MULTIFUNCTIONAL NEFARIOUSNESSES
NEUROFIBRILLARY NEWFANGLENESSES NONCERTIFICATED NONCONFIDENTIAL
NONCONFORMANCES NONFLAMMABILITY NONFUNCTIONALLY NONINFLAMMABLES
NONINFLAMMATORY NONINFLATIONARY NONINFLECTIONAL NONINFORMATIONS
NONPERFORMANCES NONPROFESSIONAL NONPROFESSORIAL NONQUANTIFIABLE
NONSAPONIFIABLE NONSIGNIFICANTS NONSPECIFICALLY NONTRANSFERABLE
OBJECTIFICATION OFFHANDEDNESSES OMNIFARIOUSNESS OPSONIFICATIONS
OVERCLASSIFYING OVERFAMILIARITY OVERFORWARDNESS PARTURIFACIENTS
PASSIFLORACEOUS PATERFAMILIASES PATRIFOCALITIES PERFECTIBILIANS
PERFECTIONATING PERFLUOROCARBON PERSONIFICATION PHOTOFLUOROGRAM
PHOTOREFRACTIVE PHYTOFLAGELLATE PONTIFICALITIES POSTTRANSFUSION
PRAYERFULNESSES PREFABRICATIONS PREFERABILITIES PREFERENTIALISM
PREFERENTIALIST PREFERENTIALITY PREFIGURATIVELY PREFORMATIONISM
PREFORMATIONIST PREMANUFACTURED PREMANUFACTURES PREMODIFICATION
PRENOTIFICATION PREPERFORMANCES PREPROFESSIONAL PRETTIFICATIONS
PROFESSIONALISE PROFESSIONALISM PROFESSIONALIST PROFESSIONALIZE
PROFITABILITIES QUANTIFICATIONS QUARTERFINALIST QUIZZIFICATIONS
REAFFORESTATION RECERTIFICATION RECODIFICATIONS RECONFIGURATION
RECONFIRMATIONS REFORMABILITIES REFORMATIONISTS REFORTIFICATION
REFRACTOMETRIES REFRANGIBLENESS REFRIGERATORIES REFUNDABILITIES
REGARDFULNESSES REMANUFACTURERS REMANUFACTURING REPROACHFULNESS
RESINIFICATIONS REVIVIFICATIONS RIGIDIFICATIONS SANCTIFICATIONS
SANGUIFICATIONS SAPONIFICATIONS SCATHEFULNESSES SCHIZOAFFECTIVE
SEMIMANUFACTURE SHAMEFASTNESSES SIGNIFICATIVELY SILICIFICATIONS
SIMPLIFICATIONS SLUMPFLATIONARY SOFTHEARTEDNESS SOLEMNIFICATION
SOLIDIFICATIONS SOOTHFASTNESSES SPEECHIFICATION STANDOFFISHNESS
STEADFASTNESSES STRAIGHTFORWARD STRATIFICATIONS STULTIFICATIONS
SUBINFEUDATIONS SUBPROFESSIONAL SUBSPECIFICALLY SULFAMETHAZINES
SULFINPYRAZONES SUPERFICIALISED SUPERFICIALISES SUPERFICIALIZED
SUPERFICIALIZES SUPERFICIALNESS SUPERFOETATIONS SYLLABIFICATION
TENTACULIFEROUS TETRAHYDROFURAN TRANSFERABILITY TRANSFIGURATION
TRANSFIGUREMENT TRANSFORMATIONS TRANSFUSIONISTS TRANSMOGRIFYING
TRIFLUOPERAZINE ULTRACENTRIFUGE ULTRAFASTIDIOUS ULTRAFILTRATION
UNDERINFLATIONS UNFAILINGNESSES UNFAMILIARITIES UNFAVORABLENESS
UNFLAPPABLENESS UNFORTUNATENESS UNHEALTHFULNESS UNIFORMITARIANS
UNINFORMATIVELY UNPROFESSIONALS UNPROFITABILITY UNQUALIFIEDNESS
UNSATISFACTIONS UNSATISFIEDNESS UNSTEADFASTNESS UNTACTFULNESSES
UNTRANSFERRABLE UNVERIFIABILITY VERIFIABILITIES VESTIMENTIFERAN
VIBROFLOTATIONS WASTERFULNESSES WEATHERPROOFING ZINCKIFICATIONS