As Regras do Ar são definidas pela ICAO e tornam-se aplicáveis com poucos desvios nos estados membros da ICAO.
O Anexo 2 da ICAO Regras do Ar define, além das regras gerais, as Regras de Voo Visual (VFR) e as Regras de Voo por Instrumentos (IFR). Os voos devem estar em conformidade com qualquer um deles.
2.2 Compliance with the rules of the air
The operation of an aircraft either in flight or on the movement area of an aerodrome shall be in compliance with the general rules and, in addition, when in flight, either with:
a) the visual flight rules; or
b) the instrument flight rules.
Capítulo 5 do Anexo 2 contém as regras do Instrument Flight.
Capítulo 4 do Anexo 2 contém as regras de voo visual.
4.1 Except when operating as a special VFR flight, VFR flights shall be conducted so that the aircraft is flown in conditions of visibility and distance from clouds equal to or greater than those specified in Table 3-1.
A Tabela 3-1 está resumida abaixo.
+---------------------------+-------------------+---------------------+-----------------------------+
| Altitude band | Airspace class | Flight visibility | Distance from cloud |
+---------------------------+-------------------+---------------------+-----------------------------+
| At and above 3 050 m | A*** B C D E F G | 8 km | 1 500 m horizontally |
| (10 000 ft) AMSL | | | 300 m (1 000 ft) vertically |
+---------------------------+-------------------+---------------------+-----------------------------+
| Below 3 050 m (10 000 ft) | A*** B C D E F G | 5 km | 1 500 m horizontally |
| AMSL and above 900 m | | | 300 m (1 000 ft) vertically |
| (3 000 ft) AMSL, or above | | | |
| 300 m (1 000 ft) above | | | |
| terrain, whichever is the | | | |
| higher | | | |
+---------------------------+-------------------+---------------------+-----------------------------+
| At and below 900 m | A*** B C D E | 5 km | 1 500 m horizontally |
| (3 000 ft) AMSL, or 300 m | | | 300 m (1 000 ft) vertically |
| (1 000 ft) above terrain, +-------------------+---------------------+-----------------------------+
| whichever is the higher | F G | 5 km** | Clear of cloud and with the |
| | | | surface in sight |
+---------------------------+-------------------+---------------------+-----------------------------+
* When the height of the transition altitude is lower than 3 050 m (10 000 ft) AMSL, FL 100 should be
used in lieu of 10 000 ft.
** When so prescribed by the appropriate ATS authority:
a) flight visibilities reduced to not less than 1 500 m may be permitted for flights operating:
1) at speeds that, in the prevailing visibility, will give adequate opportunity to observe
other traffic or any obstacles in time to avoid collision; or
2) in circumstances in which the probability of encounters with other traffic would normally
be low, e.g. in areas of low volume traffic and for aerial work at low levels.
b) HELICOPTERS may be permitted to operate in less than 1 500 m flight visibility, if manoeuvred
at a speed that will give adequate opportunity to observe other traffic or any obstacles in
time to avoid collision.
*** The VMC minima in Class A airspace are included for guidance to pilots and do not imply
acceptance of VFR flights in Class A airspace
Para fins de Gerenciamento de Tráfego Aéreo, o Doc 4444 da ICAO dá mais detalhes de como os dois tipos de vôo são tratados pelo ATC.
Os regulamentos nacionais podem desviar-se do regulamento da ICAO. Se eles desviarem, o desvio deve ser publicado na publicação de informação aeronáutica do país.