This is a sole-source solicitation for a flight-critical spare part, requiring government source approval prior to contract award. Only previously approved sources have been directly solicited. Unapproved sources may submit a proposal but must include a complete source approval request, with the evaluation of such a request potentially not being completed in time for award. The Government intends to negotiate with only one source, but will consider all proposals received within 45 days of the synopsis publication for the purpose of determining future competition. The performance location and budget are not specified.