oldandslow

Hi:

I couldn't find anything through "search" on this topic, so here goes.

I was on UA 950 on Feb 11 from SFO to IAD. The pilot made the (much-appreciated) announcement about Channel 9 being on, and then noted that during this flight ATC would be referring to us as UA 950K, or "kilo".

I've not heard of a letter suffix from ATC for a UA flight before, and I wondered what the significance of this was.

Anyone know?

Thanks in advance.

us2

If you check FlightAware, you see a number of UAL flights in there with suffixes. I think, but am not certain, that the reason is to avoid confusion with continued flights that operate with the same number, that could possibly be in the air at the same time as the arriving flight if the first segment is late. 950 runs SFO-IAD-BRU; the SFO-IAD leg is designated 950K and is operated with a different aircraft (777) than the IAD-BRU leg (763). If the SFO-IAD leg is horribly delayed and there are no or few through passengers, I could see a situation where the BRU flight would take off before the inbound segment got in from SFO. The ATC system can't handle two planes in the air at the same time with the same flight number, thus the suffix.

seauaflyer

That is correct, in the past United has used a four digit "8xxx" series flight number in these situations but I have recently noticed more extensive use of a letter after the flight number (e.g. UAL 917A).

qasr

I thought they changed to the 8XXX series when another UA flight could be in flight somewhere in the world--it is mostly a flight plan issue.

I thought the letter suffixes were mostly used for when there is another carrier with the same or similar sounding number in the same airspace. E.g. there might have been AA950 on a similar route. In that case ATC will call one AA 950 Juliet and the other UA 950 Kilo or something. I must admit though, I have only heard A/B/C suffixes used, rather than all the way through to J.

nerd

So why don't they re-number the BRU leg of the flight if/when they need to, instead of re-numbering the SFO-IAD leg?

us2

I have no idea. Perhaps there's an additional internal issue that dictates the use of the suffix. Are there any UA employees that can shed light on this?

seauaflyer

You may be right here - I just don't remember the letters being used as frequently

FWIW - right now I see four 8xxx aircraft aloft:
UAL8120 SFO-ORD
UAL8148 PDX-ORD
UAL8156 SFO-ORD
UAL8225 DEN-SNA

and two with the letters:
UAL950K SFO-IAD
UAL981L BOS-IAD

qasr

I don't get what the difference is?

nnn

Maybe it's harder, logistically, to change the flight number of a plane on an international flight plan.

redburgundy

How do you use FlightAware to show all of the UAL flights in the air at any time?

robb

I don't think ATC makes on-the-fly renumbering of flightplans (at least not commonly). If a similar-sounding flight ends up on the same frequency for another carrier, they simply emphasize the carrier name when calling for it: "American 950 American" and "United 950 United"

SANUAFlyer

Actually, with the proliferation of code-share flights (particularly with the US alliance), they have a dwindling supply of flight numbers. At some point in the future, there may be a fifth number added (flight 12345), but for right now, they are using alternate means. In fact, the strangest is the use of the same flight number for UX flights that go to and from a destination successively. (i.e. flt 7122 might be IAD-BUF and BUF-IAD in succession. It's all a scheme to conserve flight numbers.

qasr

I have heard that method, as well as a letter suffix on Ch 9. I have no idea why which is used when, I assume it is just ATC perogative?

robb

I'm just saying that changing the flightplan number (so you'd see it differently on flightaware, for example) is not a suitable choice for two flights who are temporarily on the same frequency. I think that calling the flightplan "UA 950A" would be a decision made at the time they filed, not in the air.

I suspect that what is a matter of perogative (and I think the perogative is UA's, not ATC's) is whether to call a flight UA 8XXX or UA 950A.

qasr

Ah, I was misunderstanding you--I do agree.
Almost certainly.