Air France: Typically operates nonstop BOS–CDG flights and emphasizes full-service international amenities, French cuisine onboard, and access to Air France lounges in Boston (partner lounges) and CDG. Best for passengers seeking a Parisian carrier and strong frequent-flyer benefits via Flying Blue. Delta Air Lines: Also operates nonstop flights seasonally or year-round depending on schedules, with Delta One and Comfort+ options, and SkyMiles benefits. Delta can be a good choice for U.S. transatlantic flyers with SkyTeam benefits and codeshares. One-stop options (American, United, Iberia): Often cheaper in December but require connections through domestic or European hubs; useful if nonstop seats are sold out or prices spike. When comparing, weigh nonstop convenience, seat comfort (lie-flat options), loyalty credits, and baggage allowances. CTA: Check seat maps and baggage rules for December dates and book the airline that best fits your comfort and loyalty needs.