There are very few enclosed suites with personal doors and even fewer of them are assigned to a business class seat. Here is the list:
JetBlue Mint Suite - only transcontinental, no alliance shared space, but lots of transfer partners.
Delta One Suite - plenty of transatlantic and transpacific flights, SkyTeam alliance, American Express Membership Rewards and Marriott Bonvoty transfer partners as well as several cobranded Amex credit cards. Award tickets start from 75000 Delta SkyMiles or as low as 50000 Virgin Atlantic miles.
Qatar Airways QSuites - as far as US fliers are concerned, only transatlantic routes with Doha connections to Europe and Asia. Oneworld alliance, City and Capital One transfer partners. Starts from 101500 Qatar's Qmiles, 70000 miles via AAdvantage, or 75000 Cathay Pacific.
Delta One Suite - plenty of transatlantic and transpacific flights, SkyTeam alliance, American Express Membership Rewards and Marriott Bonvoty transfer partners as well as several cobranded Amex credit cards. Award tickets start from 75000 Delta SkyMiles or as low as 50000 Virgin Atlantic miles.
Qatar Airways QSuites - as far as US fliers are concerned, only transatlantic routes with Doha connections to Europe and Asia. Oneworld alliance, City and Capital One transfer partners. Starts from 101500 Qatar's Qmiles, 70000 miles via AAdvantage, or 75000 Cathay Pacific.
