British Airways (BA) allows household accounts. BA is a possibility for a domestic trip because you can fly on American Airlines or Alaska Airlines and credit the flights to BA. The complication is that British Airways' Executive Club is not as easy to join as most. To join the Executive Club and start collecting BA Miles you must: Have booked or flown a qualifying flight in the past three months -OR- Take out and use a British Airways credit card .

The official BA credit card in USA is issued by Chase and carries a $75 annual fee, but includes 20,000 miles.

http://www.firstusa.com/cgi-bin/webc...cont&mkid=6G0Z

The problem, I think, is that each adult would need to establish a separate credit card account to join under this rule. Ordering additional cards on the same account would not create a new Executive Club number. (My understanding is that children cannot join Executive Club, except as part of a Household Account.)

There are other US credit cards that can transfer miles to BA, and in the past holding one of those (e.g. Diners Club Mastercard, Merrill+ VISA) also entitled you to join Executive Club, but I do not know if this can be done as soon as the credit card is issued.