Whether you can use two companion vouchers together depends entirely on the specific terms of the credit card or loyalty program that issued them, as well as the number of people traveling. In the most common scenario, such as the British Airways American Express Companion Voucher, you cannot stack two vouchers to fly one person for free while paying for only one; you still need one paying passenger for every "free" companion. However, you can use two vouchers on a single booking if there are four people traveling: two people pay the full Avios/cash fare, and the other two use the vouchers to fly for just the cost of taxes and fees. Some programs, like the Alaska Airlines Companion Fare, are strictly one-per-booking, meaning you would need to create two separate reservations to use two vouchers for a group of four. It is also important to check if your program allows "multi-segment" stacking; usually, these vouchers are intended for a single round-trip journey. Always read the fine print regarding "blackout dates" and "fare class availability," as these vouchers often require specific "award seats" to be open, which can be difficult to find for four people on the same flight.