Which of the following is NOT one of the three total FIRs mentioned?

Answer: D — Manchester

The three Flight Information Regions (FIRs) mentioned in the context of air traffic control in the UK include London, Scottish, and Shanwick. Each FIR serves a specific geographical area and is responsible for providing air traffic services within that region. London FIR manages airspace around the London metropolitan area, Scottish FIR covers the airspace over Scotland, and Shanwick FIR handles oceanic air traffic across the Atlantic. Manchester does not represent an independent FIR; rather, it refers to the airport or regional control services that operate under the oversight of the London FIR. Hence, it is appropriate to categorize Manchester as not being one of the three official FIRs mentioned. This distinction is crucial for understanding how air traffic services are organized and managed in the UK airspace.