Ok I was reading though part 61 today, and under 61.31 (b) (would quote it but the FAA site is being stupid today) It states the the adminstrator can autorize a flight or series of flights that would otherwise require a type rating.
Would this be where the LOAs come from? If so where does it state the minimum requirments, or is it up for the adminstrator to decide those?
There are several types of letters of authorization. To which type are you referring? 61.13(c) refers to Cat II and Cat III letters of authorization. These don't come with minimum flight experiences, but are issued on ability and performance.
You appear to be asking about an authorization to fly an aircraft requiring a type rating, without a type rating. The administrator must specifically authorize the flights in question. The individual conducting the flights must show that the operations can be conducted safely, with equivilent safety to that which would be demonstrated by a pilot who has satisfactorily met the type rating requirments.
The flight may only be a ferry flight, training flight test flight, or a practical test for a pilot certificate or rating. It can only carry required crew members, cannot involve compensation or hire, and must be conducted within the United States. I have copied 61.31(b) below.
As also you asked about regulation covering LoA's, the following apply:
91.175(k) refers to the use of a LoA in substituting for the inner marker during Cat II and Cat III operations.
91.189(f) prevents a person from landing during a Cat III approach without a DH, without a LoA.
91.213(a)(2) applies the use of the LoA for a minimum equipment list in operating with inoperative equipment or instruments, and sets the premise that a LoA and MEL for an aircraft constitute an STC. (Eeaieeaiou. M-O-U-S-E...too much alphabet soup in aviation).
91.531(b) provides for the issuance of a LoA in lieu of a second in command for certain aircraft.
Part 91 Appendix G, section 3(a) specifies that either ops specs or a LoA may be used by a an operator in RVSM airspace.
Part 91 Appendix G Section 7 provides that the administrator may remove a LoA for operations in RVSM airspace if non-compliance is determined.
91.33(c) covers the issuance of a LoA to a certificate holder for the purpose of conducting proving tests.
Part 129.14(b)(4) referencs the use of foriegn air carriers with respect to a LoA by the Administrator, of a MEL.
Additionally, a LoA may be issued for special instrument proceedures. The Administrator may issue a LoA for a variety of other specific uses to an individual, or individual operator.
§ 61.31 Type rating requirements, additional training, and authorization requirements.
(b) Authorization in lieu of a type rating. A person may be authorized to operate without a type rating for up to 60 days an aircraft requiring a type rating, provided -
(1) The Administrator has authorized the flight or series of flights;
(2) The Administrator has determined that an equivalent level of safety can be achieved through the operating limitations on the authorization;
(3) The person shows that compliance with paragraph (a) of this section is impracticable for the flight or series of flights; and
(4) The flight -
(i) Involves only a ferry flight, training flight, test flight, or practical test for a pilot certificate or rating;
(ii) Is within the United States;
(iii) Does not involve operations for compensation or hire unless the compensation or hire involves payment for the use of the aircraft for training or taking a practical test; and
(iv) Involves only the carriage of flight crewmembers considered essential for the flight.
(5) If the flight or series of flights cannot be accomplished within the time limit of the authorization, the Administrator may authorize an additional period of up to 60 days to accomplish the flight or series of flights.