From time to time, flags become more or less favorable, with some being white, grey, or black-listed, with white being favorable flags while black represents flags with poor reputations that could lead to problems with ports, lenders, and insurances companies.
Historically, Panama and Liberia have been well-known open registries and remain on the white list, while the Marshall Islands, also having white list status, is gaining popularity and the Marshall Islands Ship Registry could be a good option for a flag state. While the USCG has citizenship requirements, the Marshall Islands Ship Registry has no such requirements and affords right to operate in US waters.