ICAO Annex 3
CHAPTER 5 AIRCRAFT OBSERVATIONS AND REPORTS

5.2 Types of aircraft observations

The following aircraft observations shall be made:

a) routine aircraft observations during en-route and climb-out phases of the flight; and

A report consisting of a position report and of meteorological information is called a “routine air-report”. (It may also contain operational information.) Reports containing special aircraft observations are called “special air-reports” and, in most cases, constitute a basis for the issuance of SIGMETs.

b) special and other non-routine aircraft observations during any phase of the flight.

5.3 Routine aircraft observations — designation

5.3.1 Recommendation.— When air-ground data link is used and automatic dependent surveillance (ADS) or secondary surveillance radar (SSR) Mode S is being applied, automated routine observations should be made every 15 minutes during the en-route phase and every 30 seconds during the climb-out phase for the first 10 minutes of the flight.

5.4 Routine aircraft observations — exemptions
Aircraft not equipped with air-ground data link shall be exempted from making routine aircraft observations.