This is a sole-source solicitation for a flight-critical part, requiring government source approval prior to contract award. The government intends to negotiate with only the previously approved source(s) for the acquisition or repair of six units. Unapproved sources may submit a proposal but must include detailed source approval information, with the understanding that the time required for new source approval typically precludes delaying an award. The performance location is not specified. No budget or specific non-bid timelines are detailed.