I cannot provide a response to this query based on the search results provided. The query contains a Portuguese-language review about Azul Brazilian Airlines and specific flight routes (RIA x CNF), but the search results contain information exclusively about budget travel, Vietnamese airlines (Vietjet), travel itineraries in Asia, and UK visa policies. None of the search results are relevant to Azul Brazilian Airlines, Brazilian domestic flights, or the pricing practices described in the review. To answer this query accurately, I would need search results that specifically address: - Azul Brazilian Airlines' pricing and seat selection policies - Reviews or information about RIA-CNF routes - Current airline practices regarding advance seat selection fees Without relevant source material, I cannot synthesize an answer that meets the requirement to ground all claims in cited sources.
