JS,

I would suggest that small airfield codes are all a lot more useful now that computing is taking over!

For instance, a popular flight from here (Strathaven Airfield) to Bute, appears in a flight plan - mandatory and now in a computer based format if one wants to transit controlled airspace - as from XXXX to XXXX.

Not very helpful!

Small unlicensed airfields now have a surprising number of users. To put it bluntly, most big airports with ICAO codes in central Scotland just don't seem to want private flyers, so they have had to move elsewhere.

It's mandatory to file a flightplan from Strathaven to Bute? Since when?

(I know about the need to submit "a flightplan" when crossing CAS, but that's certainly not a requirement for a computerised FPL using airfield codes or ZZZZ and then "DEP/" or "ARR/" in Field 18 - you can do it verbally over the radio, as 99% of people do)

Since if you want to route direct! No need to file from Strathaven to Bute if you keep out of controlled airspace.

(and not allowed in this summer, anyway!)

Was told the tower just put in the XXXXs when you asked for zone transit prior by phone (as they requested at GLA and EDI after assistants were found to be unnecessary!) or the old-fashioned over the radio way.

So didn't seem helpful there not being an ICAO code for Bute (or Strathaven).

Bute is a classic example where if you take annual movements and divide by 365, you won't have much of a daily average. Yet on a nice day it can be busy busy!

But there's no need to - and nobody would - file an ICAO FPL even if you do route direct. You'd just call up on the radio for a Class D transit, as is standard.

Whether there's an airfield code or not makes no practical difference.

I am not sure what you mean by that. I have had a home computer for nearly forty years but would never want to file a flight plan for a local flight. I think you will find computers took over decades ago:ok:

Nearly everywhere on the planet has its own unique code. Latitude and longitude. Strathallan is 56.3252° N, 3.7468° W

Why try to dream up new ones?

(Exceptions being the N and S poles)

US airfields seem to have codes - 3 group mix of letter and numbers for minor airfields. Which are ICAO compliant with the K prefixed.
(Thread drift Somewhere in Mexico had a 5 item code. Someone flight planned to it from US. The guy entering it into the computer didn't notice, and subsequent identifiers overflowed. Chaos. Late 90s, October.)

XXXX would be rejected by the system, it should be ZZZZ.

Same applies for Item 18 Destination Aerodrome.