Most aviation rules come with an escape hatch. A state that cannot meet an ICAO standard files a difference, writes its own version, and carries on. The system is built to flex, because 193 countries will never do everything the same way. Annex 2 is the exception to that flexibility -- and over the open ocean, it is the exception that has no exception at all.
Annex 2 to the Convention on International Civil Aviation is called the Rules of the Air, and it governs the most basic question in flying: when two aircraft share the same sky, who does what? It is short, blunt, and unusually rigid. While most Annexes mix binding Standards with softer Recommended Practices, Annex 2 contains Standards only. There is no "recommended" right of way, no advisory version of a collision-avoidance rule. You either follow it or you are operating unsafely.
Why "no exceptions" is literally true
The phrase is not marketing. It comes straight from the treaty. Article 12 of the Chicago Convention obliges every contracting state to keep its own rules of the air uniform, to the greatest possible extent, with those established under the Convention. Then it goes further: over the high seas, the rules in force shall be those established under this Convention -- meaning Annex 2 itself, with no national overlay. Article 12 also makes each state responsible for prosecuting anyone who violates the applicable regulations.
Pull those threads together and you get the defining feature of Annex 2. Inside a state's own airspace, it may file differences like any other Annex, though in practice states keep very close to it. But over the high seas -- the oceanic airspace beyond any country's territory, which covers most of the planet -- there is no sovereign to write local rules, so ICAO's rules apply directly and uniformly. No state may file a difference there, because there is no national jurisdiction to differ from. A pilot crossing the North Atlantic and a pilot crossing the South Pacific are flying under the exact same right-of-way rules. That is the whole point.
For developers, the closest analogy is a protocol with no permitted local extensions over the shared backbone. Everyone implements the same spec, byte for byte, because the moment two parties interpret "who yields" differently, the connection -- here, two aircraft -- collides.
The general rules of flight
Before it gets to traffic, Annex 2 sets the ground rules for how an aircraft may be flown at all. The first is almost philosophical: an aircraft must not be operated in a negligent or reckless manner that endangers life or property. Everything else builds on that duty of care.
From there the general rules cover a long list of situations, and they read like the accumulated lessons of a century of flying:
- Minimum heights -- aircraft may not fly so low over people or property as to create a hazard, except when taking off or landing.
- Cruising levels -- the level at which a flight is conducted is expressed by reference to a standardised system, so that traffic going opposite directions is vertically separated.
- Dropping and spraying, towing, parachute descents, aerobatic flight, and formation flights -- each permitted only under defined conditions, with formation flying requiring prior arrangement among the pilots.
- Prohibited and restricted areas -- aircraft must not enter them except in accordance with the conditions the establishing state has published.
None of this is exotic. It is the connective tissue that keeps ordinary operations from turning into hazards.
Right of way: the heart of the Annex
The collision-avoidance section is where Annex 2 earns its keep. It establishes a clear hierarchy and a set of geometric rules, so that in any encounter both pilots already know, without negotiation, who is expected to give way.
The rules by geometry are these. When two aircraft are converging at about the same level, the one that has the other on its right gives way. In a head-on approach, both turn right. When overtaking, the faster aircraft alters course to the right to pass, and the aircraft being overtaken keeps the right of way. On approach to land, an aircraft on final or landing has priority over one in flight, and the lower of two approaching aircraft has the right of way -- with a safeguard against cutting in front of one that is on final.
Layered on top is a give-way hierarchy by aircraft type, reflecting maneuverability. A power-driven heavier-than-air aircraft -- an ordinary aeroplane -- gives way to airships, gliders, and balloons. Among those, the order continues: airships give way to gliders and balloons, gliders give way to balloons. A balloon, which can do little but drift, has right of way over nearly everything. Aircraft towing or refuelling others also get priority because of their limited ability to maneuver.
And then the rule that overrides all the others:
Having the right of way never relieves a pilot of the responsibility to do everything possible to avoid a collision.
Right of way is not a license to hold course into a crash. It tells you who is expected to move first -- not who is entitled to stop looking.
Lights
So that these rules can be applied at night, Annex 2 specifies the navigation and anti-collision lights an aircraft must display, and when. The red-on-the-left, green-on-the-right convention is what lets a pilot read another aircraft's heading in the dark and apply the converging and head-on rules correctly.
Flight plans
A flight plan is how the system knows you intend to be somewhere. Annex 2 sets out when one is required -- always for IFR flights in controlled airspace, and in other cases defined by the state or the airspace -- and what it must contain: aircraft identification, route, levels, timing, and more. The pilot is expected to adhere to the current flight plan, to report and coordinate in-flight changes, and, critically, to close the plan on arrival. That last step is not paperwork for its own sake: an unclosed flight plan is one of the triggers that can launch search and rescue, on the assumption that an aircraft that never reported arriving may be down.
VFR and IFR: two ways to fly
Every flight operates under one of two sets of rules, and Annex 2 defines both. The split is fundamental enough that it shapes the entire structure of air traffic services.
Visual Flight Rules
Under Visual Flight Rules (VFR), the pilot navigates and separates from other traffic by looking out the window. This is only safe in visual meteorological conditions (VMC) -- weather good enough to see and be seen. Annex 2 prescribes VMC minima in terms of flight visibility and distance from cloud, and these vary by airspace class and altitude: more demanding where traffic is dense and faster, somewhat relaxed at lower levels in less busy airspace. VFR is not permitted in some circumstances at all -- above certain levels, in controlled airspace except under a special VFR clearance, and states may restrict or prohibit night VFR. The logic is simple: see-and-avoid stops working when you cannot see.
Instrument Flight Rules
Under Instrument Flight Rules (IFR), the pilot flies by reference to instruments and is separated from other traffic by procedure and by air traffic control, not by eyesight. IFR is what makes flight in cloud, at night, and at high altitude routine and safe. Annex 2 sets rules that apply to all IFR flights -- minimum levels, equipment expectations -- and distinguishes IFR operated inside controlled airspace, where it is subject to ATC clearance and separation, from IFR outside controlled airspace, where the pilot carries more of the separation responsibility. Airline flying is essentially all IFR.
Clearances, signals, and the rules' relationship to ATC
Air traffic control clearances and the rules of the air work together, but Annex 2 is careful about the boundary. A clearance authorises a flight to proceed under conditions ATC specifies; it does not override a pilot's overriding duty to avoid a collision or to keep the aircraft safe. If accepting a clearance would be unsafe, the pilot is expected to say so.
The Annex also standardises the signals aviation falls back on when normal communication is unavailable: distress and urgency signals, light and pyrotechnic signals from the ground, and the marshalling signals used to direct an aircraft on the apron. These exist precisely for the moment the radio fails -- a common visual vocabulary so that meaning survives even when voice does not.
Interception: the gravest case
Annex 2 carries the rules for the interception of civil aircraft, and they begin from a principle that has been paid for in blood: interception should be avoided, and undertaken only as a last resort. When it does happen, standardised visual signals between the intercepting and intercepted aircraft let pilots who share no common language communicate intent -- follow me, you may proceed, land at this aerodrome.
This connects directly to Article 3 bis of the Chicago Convention, which affirms that states must refrain from resorting to the use of weapons against civil aircraft in flight. Article 3 bis was adopted after the 1983 destruction of a civil airliner that had strayed into prohibited airspace, an event that made the international community codify in the treaty what should never have needed saying. The interception provisions of Annex 2 are the operational expression of that principle.
Separately, the Annex addresses unlawful interference: a pilot subjected to it is expected, as far as possible, to continue operating safely and to alert the relevant authorities, with procedures designed to make the situation recognisable to ATC.
How states put Annex 2 into law
Because Article 12 demands uniformity, national implementations of Annex 2 sit closer to the source than most Annexes.
- Saudi Arabia enacts its rules of the air through the General Authority of Civil Aviation (GACA), aligned to Annex 2.
- The United States codifies them in 14 CFR Part 91 -- right-of-way rules in 91.113, VFR weather minimums in 91.155 -- the general operating rules every US pilot knows.
- Europe went furthest toward harmonisation with the Standardised European Rules of the Air (SERA), established by Commission Implementing Regulation (EU) No 923/2012, which transposes Annex 2 directly into a single rule set applied across European states instead of leaving each to write its own.
SERA is worth pausing on. It is, in effect, Annex 2 turned into directly applicable law across a continent -- the clearest demonstration of how far the uniformity principle can be pushed when the political will exists.
Where the friction remains
For a rulebook built on uniformity, Annex 2's hardest problems are all about the places uniformity slips. Applying airspace classes consistently across borders is harder than it sounds, because the same class letter can feel different from one state to the next. Special-VFR and night-VFR permissions vary, so what a pilot may legally do in one country's marginal weather differs in the next. And keeping interception procedures truly standardised across the world's air forces and civil authorities is an ongoing effort, not a solved problem -- which matters most in exactly the rare, high-stakes moment the rules exist for.
Annex 2 has stood at its 10th Edition (July 2005) for a long time, maintained through amendments rather than re-issued, so anyone citing a specific provision should check the current amendment against the consolidated text. But its endurance is the tell. The rules of the air change slowly because the physics of two aircraft meeting in the sky does not change at all. Somewhere over the middle of an ocean right now, with no controller watching and no state's law in force, two crews are trusting that the other knows to turn right. Annex 2 is the reason that trust is justified.