There is a reason for everything in the aviation industry. From the number of crews in an aircraft to the type of meal both the pilots consume. And the numbers and letters you see on your boarding pass are no random combination. Every airline uses a specific system to scribe letters and numbers to every flight.
The letter combinations are always alphanumeric. For example, Air Asia Uses AK, Malaysia Airlines uses MH, Malindo OD, etc.
Although each airline has its own rules. They are not allowed to use more than 4 digit numbers which are from 1 to 9999. They can assign each number however they want it as long as its a combination of two alphabets and not more than 4 numbers. How these numbers bring significance to the operation of an airline. As passengers, it does not mean anything to us.
A flight number, when combined with the name of the airline and the date, identifies a particular flight. This callsign should not be confused with the tail number of the aircraft, although both can be used as a call-sign as used in general aviation. A particular aircraft may fly several different flights in one day, and different aircraft may be used for the same flight number on successive days. A number of conventions have been developed for defining flight numbers, although these vary widely from airline to airline.
Eastbound and northbound flights are traditionally assigned even numbers, while westbound and southbound flights have odd numbers.
For Example, SQ516 Operates from Singapore To Kolkata. 516 is an even number which means its either operating towards NORTH/WEST and returns flight is going to be +1 (SQ517) as it is going to be in the reciprocal direction
Other airlines will use an odd number for an outbound flight and use the next even number for the reverse inbound flight.
For destinations served by multiple flights per day, numbers tend to increase during the day. Hence, a flight from point A to point B might be flight 6266 and the return flight from B to A would be 6227, while the next pair of flights on the same route would usually be assigned codes 6228 and 6229.
Generally, the lower the flight number, the more important that route is to the airline. The very important flight number likely relates to the airline’s history. Malaysia Airlines’ very first important destination is London is MH01.
Interesting points to add, airlines usually will retire particular flight numbers that involve in major tragedy.
MH will use single to triple digits flight numbers for regional and international flights and 4-digits flight numbers for domestic flights.
Due to superstition, they don’t really operate on 13 or 666. Certain flight numbers may not be used due to certain incidents such as AA11 after the September 11, 2011, attack. To be closer, it would the MH370 & MH17 tragedy.
What about code-sharing flights?
You bought a ticket for a flight. You show up to the airport and find your flight number on the departures board. So far, everything is normal. But when you show up to the gate, the airline you thought you were flying is nowhere to be seen and it’s a different airline’s logo on the side of the plane. You just experienced codeshare.
This provides clearer routing for the customer, allowing a customer to book travel from point A to C through point B under one carrier’s code, instead of a customer booking from point A to B under one code, and from point B to C under another code. This is not only a superficial addition as cooperating airlines also strive to synchronize their schedules.
There are several types of code-sharing arrangements:
- Block space codeshare: A commercial (marketing) airline purchases a fixed number of seats from the administrating (operating/prime) carrier. A fixed price is typically paid, and the seats are kept away from the administrating carrier’s inventory. The marketing airline decides on its own which booking classes the seats are sold in (the block of seats are optimised just like another aircraft cabin).
- Free flow codeshare: The airlines’ inventory and reservation systems communicate in real-time by messaging, commonly IATA AIRIMP/PADIS messaging (TTY and EDIFACT). A booking class mapping is defined between the airlines. No seats are locked to any of the airlines, and any airline can sell any number of seats.
- Capped free flow: Basically the same as above, but a capping (maximum number of seats) are defined for each of the marketing airlines participating in the codeshare with the administrating carrier.