No, your husband cannot use your United MileagePlus number for his own flight bookings; frequent flyer accounts are strictly individual and must match the name on the traveler's government-issued ID. If you attempt to put your number on his ticket, the system will reject it, or he will simply not earn any miles for the flight. However, United Airlines recently introduced "Miles Pooling," which is the perfect solution for couples. This feature allows you and up to four other friends or family members to combine your miles into a single shared account for free. Once pooled, the miles can be used to book award flights for anyone in the group. If you have a high balance and he has very few miles, you can also use your miles to book a ticket for him by simply entering his name as the passenger during the checkout process; the miles come from your account, but the ticket is in his name. Additionally, if you hold United Premier status, he can only share your benefits (like free checked bags or priority boarding) if he is booked on the same reservation as you.