Aircraft Rollover Charts - how do they work?

Factual Questions
1

How do airlines decide which aircraft flies to a certain destination and then onwards to another destination ?
As in an aircraft operating as Flt123 reaches destination X and then flies to another station Y as Flt 124 and so on non stop.
Example
Aircraft D-CNDH Airbus 333 will do SEA-FRA and then return as FRA - SEA or might go FRA-DEL and then operate DEL-MUC ?
How does the rollover chart compensate when an aircraft is delayed considerably or goes AOG ?
When you count the number of aircraft and the number of stations they fly to, there should some sort of logic behind the planning. It is mindboggling to me.

2

I don’t have a GQ-worthy answer, but there are a few general principles :

  • Airlines have a lot of data to back up their decisions on plane assignments for routine flights. On a normal weekday, N people are going to want to fly from point A to point B at 7:00 AM, and N-3 people from point B to point C at 9:30 AM. On a normal Friday, it’s 17% more, etc.
  • Every night, it’s possible to wipe out most delays that accumulated during the day.
  • Airlines operate on thin margins, and need to ensure their planes are as full as possible (or at least have someone paying for almost every seat). They use overbooking to make it happen. Overbooking penalties are part of the equation.
  • On special occasions (like Thanksgiving in the U.S.) the planning is different but it still fails often and people do miss connections, etc. This is not pleasant for anyone, but people expect it to happen to some extent. It may not be necessary (from the airline’s point of view) to add enough planes to make everybody happy.
  • It’s possible for an airline to know (from its data) that there will probably be 1 in 179 flights that can’t take off because of mechanical stuff. That can be mitigated by having a small number of available spare 737s or A330s (with crews) at the main hubs.
3

Looks like it’s a big mathematical modeling exercise, and something where there’s still a lot of work being done to optimize it.

Here’s a PDF that talks about some of the considerations:

4

It’s not just the equipment, it’s the crew too. Crew are only certified to fly certain aircraft (or common type rated aircraft) at one time.

For example, United may have a crew base for 777 and 787 pilots in Denver, but only 767 pilots in Cleveland. On a flight with a B777 from DEN to CLE, they need to plan the flight to return to a 777 base before the pilots time out or deadhead the return pilots with the outbound flight.

5

Thank you so much for this : )

6

For me the more than pax and crew, is how they decide where an aircraft is going to fly to next.
Ex
KLM
PHAOB does YYC-AMS. Then it might do AMS-EBB then return doing EBB-AMS and then it does AMS-ACC and so on. That is the type of rollover I meant. :slight_smile:
When we extrapolate that over a fleet, it would have been quite a feat to do that on paper before computers took over. Like weight and balance using a slide rule type device before visual load control software made it a breeze.