Same Flight... Different Flight Numbers

[chexfan]

OK, I'm sure this is a silly basic question for y'all experts!

I'm tracking a flight right now- UA916 (SEA-IAD). There are no problems getting its information from united.com.

But if I go to a website such as trackaflight.com it only shows the IAD-FRA segment of the flight. It shows the SEA-IAD segment as UA8158.

What causes this discrepency? Thanks in advance.

 

[faver]

it might just be a issue with that tracking site. or someone got it wrong input. or right input wrong numbers.

um could be a few things. couldn't really say, sounds like just a blip in the system. or something. or u maybe got the wrong carrier. i couldn't say. wouldn't worry about it to hard.

 

[chexfan]

OK, Lemme ask this: What happens if a 1-stop flight has a change of a/c AND a delay?

For example, UA938 is a "1-Stop Flight" flight from SEA to LHR with a 1h 45m stop (& a/c change) at ORD.

The flight is a B757 from SEA-ORD and a B777 from ORD to LHR. What happens to the flight numbers if SEA-ORD is 2 hours delayed and ORD-LHR is on time? Surely the outbound flight to LHR and the inbound flight from SEA can't both be UA938.

Does my scenario make sense?

 

[mweiss]

Ya know, I've often wondered about this one myself. Imagine what it'd be like for ATC if the two were coincidentally in the same sector!

 

[faver]

well if they make that the normal routine for there airline, might as well just call it a change of planes, sounds like a stupid idea but whatever works i guess. and if they did have that sneario then that other plane should be held til that plane gets there or the whatever but the flight number should be different your not suppose to have two of same flight numbers. so not sure what happened.

interesting though

if you find out for sure, let us know.

 

[jimntx]

I remember working a flight from SAN-ORD as the #1. I had to announce, "Ladies and Gentlemen. Welcome aboard American Airlines flight (whatever) from San Diego to Chicago with continuing service to Charles De Gaulle airport in Paris." The part that made me feel sorta silly was the fact that we were on an MD-80 at the time! There would obviously be a change of equipment at ORD; so, if the inbound was late, there would have been no reason to delay departure of the flight to CDG. I'll ask someone at AA what they would have done in such a situation and report back. It's an interesting question.

 

[jimntx]

The answer I got from AA is...
1. If the inbound leg was running late, the outbound leg would NOT be delayed if ready for departure.
2. In the event that inbound leg was still in the air when the outbound leg departed, ATC would append a letter to the flight number of the outbound leg to differentiate from inbound leg. I.E. Inbound is flight 10; outbound is flight 10A.

 

[DCT JVL]

OK, Lemme ask this: What happens if a 1-stop flight has a change of a/c AND a delay?

For example, UA938 is a "1-Stop Flight" flight from SEA to LHR with a 1h 45m stop (& a/c change) at ORD.

The flight is a B757 from SEA-ORD and a B777 from ORD to LHR. What happens to the flight numbers if SEA-ORD is 2 hours delayed and ORD-LHR is on time? Surely the outbound flight to LHR and the inbound flight from SEA can't both be UA938.

Does my scenario make sense?

This is probably the scenario you saw on the flight tracker. The 8100 flight number is a "radio number" and used for ATC purposes to prevent flight number confusion. The delayed flight example you use is usually the most common circumstance where a radio number is used, but sometimes we'll file a radio number when ATC asks us to. For example, if there are two flights from different airlines with the same number in the same airspace on a daily basis, ATC will ask one of the airlines to switch up. The last thing ATC wants is two flights with similiar or identical flight numbers in the same airspace at the same time. These numbers are resticted to radio use since it would cause way too much confusion to the passengers if you were changing flight numbers on a tactical basis. Besides, so much else is keyed into the planned flight number, you can't just go a switch it on daily basis.

 

[DCT JVL]

FYI, 916 continues to FRA as a 777 from IAD.

 

[Art at ISP]

UAL uses 8000 series flight numbers for ATC only when there is the chance that 2 aircraft operating the same flight number will be in the air at the same time. Most domestic legs of international flights will have an 8000 series flight number for ATC communications.

The reason is exactly as above--to avoid confusion when both aircraft operating the flight are airborne at the same time.

This is common practice at UA.

I hope this helps.