The Terminal Aerodrome Forecast (TAF) is one of the most prominent and widely accepted forecasting tools for flight planning. The reliability of this instrument is crucial for its practical applicability, and its quality may further affect the overall air transport safety and economic efficiency. The presented study seeks to objectify the assessment of the success rate of TAFs in the full breadth of their scope, unlike alternative approaches that typically analyze one selected element. It aspires to submit a complex survey on TAF realization in the context of ANNEX 3 (a regulation for Meteorological Service for International Air Navigation issued by the International Civil Aviation Organization (ICAO)) defined methodology and to provoke a discussion on the clarification and completion of ANNEX 3. Moreover, the adherence of TAFs to ICAO ANNEX 3 (20th Edition) is examined and presented on the example of reports issued in the Czech Republic. The study evaluates the accuracy of TAF forecast verified by Aerodrome Routine Meteorological Report (METAR) and Special Meteorological Report (SPECI), whose quality was assessed first. The required accuracy of TAFs was achieved for most evaluated stations. A discrepancy in terms of formal structure between actually issued reports and the ANNEX 3 defined form was revealed in over 90% of reports. The study identifies ambiguities and contradictions contained in ANNEX 3 that lead to loose interpretations of its stipulations and complicate the objectification of TAF evaluation.