Whether the first carry-on bag is free depends entirely on the airline's business model and the specific fare class you purchased. Most "legacy" carriers like Delta, American, and United (for standard economy and above) include one full-sized carry-on bag and one personal item for free. However, if you book a "Basic Economy" ticket on United or JetBlue, a full-sized overhead bin bag is often excluded, and bringing one to the gate can result in a heavy fine and a checked bag fee. Conversely, "Low-Cost Carriers" (LCCs) like Spirit, Frontier, and Ryanair almost never include a free carry-on bag; they only allow a small personal item that fits under the seat in front of you. Southwest Airlines remains a notable exception in the U.S., allowing two checked bags and a carry-on for free. Internationally, weight limits for "free" carry-ons are often strictly enforced at 7kg to 10kg. Always check your specific "Fare Rules" during booking, as the "free" status of a carry-on is no longer a universal industry standard but a tiered perk.