ATS Routes and Classifications
Route designators
ATS routes are designated as airways with letters and numbers, and their classification indicates whether they are controlled, advisory or unclassified. Know the meaning of the prefix letters, the use of one-way routes, and the role of significant points, including named waypoints and NAVAID-based fixes. RNAV routes and PBN specifications are increasingly relevant.
Route use and flight levels
Know the semicircular rule for cruising levels, the table of cruising levels for IFR and VFR, and the quadrantal rule where applied. Bolivia uses feet, with transition altitude and transition level published in the AIP. Below the transition altitude, altitude is used; above, flight level. The transition layer is the space between them.
Traps in questions
A common trap is applying the wrong cruising level table to VFR or IFR, or forgetting that magnetic track determines the level. Another is confusing the transition altitude with the transition level, or assuming a route is controlled when it is advisory only. Questions may also test whether a waypoint is a reporting point.
Rule of thumb
For semicircular levels: tracks 000-179 use odd levels, 180-359 use even levels, with the table giving the exact values. Worked example: an IFR flight tracking 090 magnetic at FL 330 is correct because 090 falls in 000-179 and FL 330 is an odd level. If it were tracking 270, the correct level would be even, such as FL 320.