When the air traffic controller has several aircraft in his area of responsibility, he will decide to give the clearances in a certain order. This document will help you to understand the group of priorities and why we need them.
According to ICAO, all communication between pilots and air traffic controllers can be categorised into 6 categories of messages depending on the priority of information being transmitted (priority set by order):
1. DISTRESS: serious and/or imminent danger, requiring immediate assistance (MAYDAY).
2. URGENCY: condition concerning the safety of an aircraft (PAN,PAN or PAN, PAN MEDICAL)
3. DIRECTION FINDING
4. FLIGHT SAFETY
6. FLIGHT REGULARITY
DISTRESS message is the highest priority and FLIGHT REGULARITY message is the lowest priority
The DISTRESS and URGENCY messages should be clear for all air traffic controllers (read the relevant documentation to understand the messages and applicable procedures).
The DIRECTION FINDING messages should be not applicable for IVAO as they refer to direction-finding stations which are not simulated in the IVAO network. (But for IVAO, in this situation, assistance requested by an aircraft in order to know the bearing toward the airport can be considered to be similar to this type of message.)
The FLIGHT SAFETY messages shall comprise the following:
The METEOROLOGICAL messages shall comprise all meteorological information to or from aircraft other than the meteorological messages concerned in the FLIGHT SAFETY message.
In the IVAO network, some air traffic controllers think that instrument flight rule flights (IFR) have priority over visual flight rule flights (VFR).
In the regulations, there is no rule stating this.
In real life, the air traffic controller will only facilitate the commercial flight in order to reduce the route length and the delay for landing. For Airline Companies, time is money and one go-around creates extra cost.
In conclusion, the controller will usually take care of commercial flights before private flights which have less constraints, and give the traffic priority in function of aircrafts' position and performance, but not in function of flight rules as a first criterion.
One go around for an IFR requires a complete new IFR approach in most cases, which can take more than 20min extra flight time. One go around for a VFR only requires reintegration into the aerodrome circuit which can generate only 5 to 10 minutes extra flight time.
The priority of traffic should follow this order:
Pay attention that many beginners in ATC too often give flight clearances and do not care about traffic in flight or moving on the ground which are more important.
In conclusion, a simple formula of priority management for aircraft handling reads: Emergency >Urgency >Aircraft flying >Runway handling >Taxi ground >Pushback >Flight Clearance