On a Jeppesen enroute chart, what does the 'T' signify in an altitude like 2500T?

The designation 'T' in an altitude such as 2500T specifically indicates a Minimum Obstacle Clearance Altitude (MOCA). This is a critical component in ensuring safety for aircraft during flight, particularly in areas where terrain could pose a risk. MOCA provides a vertical clearance above any obstacles or terrain along a route, which is necessary for pilots to maintain a safe altitude while navigating.

The indication of 'T' helps pilots quickly identify that the given altitude is specifically constructed to provide adequate barrier against obstacles. This ensures that during their enroute phases, they can follow published route structures with confidence that they are maintaining a safe altitude relative to the terrain and obstacles around them.

Understanding this designation is vital for flight planning and navigation, as it directly impacts decision-making in regards to altitude management. This is especially important in mountainous or uneven terrain where ensuring appropriate clearance is crucial for safe aircraft operations.