Which of the following is NOT a restriction for uncontrolled airfields with LOAs?

The choice indicating "Must fly right-hand patterns" is not a restriction for uncontrolled airfields with Letters of Agreement (LOAs). Typically, the rules governing airspace operations, including the patterns in which aircraft operate at uncontrolled airfields, do not mandate specific directional patterns like right-hand patterns unless explicitly stated in the LOA. Uncontrolled airfields often allow for flexibility in maneuvering, and pilots can choose their patterns based on factors like wind direction and traffic, unless there are specific guidance or limitations provided in the LOA or local procedures that dictate otherwise.

The other options present real restrictions commonly enforced at uncontrolled fields. For instance, limiting the number of aircraft in the pattern helps maintain safety and separation. The restriction to single aircraft operations without formation is also significant, as it reduces complexity and the risk of mid-air collisions, particularly where radio communication may not be as reliable. Furthermore, imposing a maximum airspeed ensures that aircraft operate within safe limits, helping to prevent conflicts with other air traffic and ensuring safe operations during approach and landing phases.