When flying along IR 644, what should a pilot expect?

When flying along IR 644, pilots can expect IFR training flights that occur above 1500 feet AGL and at speeds exceeding 250 knots. This expectation aligns with the characteristics of instrument routes, which are specifically designed to facilitate instrument flight rules operations. These routes enable structured flight paths that allow for more efficient management of IFR traffic, especially in busy airspaces.

Instrument flight rules dictate that aircraft operating under IFR maintain specific altitudes and airspeeds for safety and navigation purposes. Therefore, these specific requirements explain why the chosen answer is appropriate: it reflects the nature of IR 644 as a route primarily utilized for IFR operations, which often involve higher altitudes and faster speeds than typical VFR training flights would entail.

VFR training flights, which are generally conducted below a specific altitude and at lower speeds to ensure safety and maneuverability, would not typically be expected on an IFR route designed for more complex flight operations. This makes the other options less applicable in the context of what pilots can anticipate while flying along IR 644.