Rules of the Air and Air Traffic Services
This is the most numerically testable domain: VMC minima, cruising levels, right of way, and airspace class behaviour.
The source rules
Annex 2 (Rules of the Air) is implemented in Europe by SERA (Reg. 923/2012). Annex 11 governs air traffic services; SERA and Annex 11 together define clearances, separation and the alerting service.
Airspace classes
Classes A to G: A to E are controlled, with class F advisory and class G uncontrolled. In class A only IFR is permitted; in B to D both IFR and VFR are allowed with varying separation; in E IFR is separated from IFR, VFR receives traffic information; in F and G no clearance is required and separation is the pilot's responsibility.
VMC minima (SERA, below 10 000 ft)
At and above 10 000 ft: 8 km flight visibility, 1,500 m horizontal and 300 m (1,000 ft) vertical distance from cloud. Below 10 000 ft: 5 km, 1,500 m and 300 m. At and below 900 ft AMSL: 5 km, clear of cloud and in sight of the surface. VFR flight at night requires the applicable national conditions.
Cruising levels
The semicircular rule assigns magnetic tracks 000-179 odd thousands plus 500 ft, and 180-359 even thousands plus 500 ft, with the table varying by airspace and by quadrant, and RVSM 1,000 ft separation between FL290 and FL410.
Right of way
Converging aircraft of the same category: the one on the right has right of way. Head-on: both turn right. Overtaking: the overtaking aircraft keeps clear. Landing: lower aircraft has priority; aircraft on final or on the ground have priority over taxiing aircraft.
Worked example
Cruising VFR at 5,500 ft AMSL in class G, cloud base 4,000 ft: 5 km visibility and 1,500 m/300 m cloud distances apply, so flight is legal provided the aircraft stays clear of cloud and the surface is in sight at the lower levels.
Traps that cost marks
Using 8 km below 10 000 ft; forgetting that class F is not controlled; assuming a VFR flight in class G needs a clearance.