No, because it's not possible to fly non-stop from LAS-LGA. You should, however, be able to SDC to LAS-JFK or LAS-EWR.

Apologies for the bad example.
My understanding from your answer is that I can sdc from connecting flight to direct flight if available as long as the departure and destination are the same or co-located.
Delta does not allow this kind of sdc.
Thanks.

AFAIK it is permitted on JetBlue but you’ll pay a $75 fee per person unless you’re a Mosaic.

Or you could by a flex/plus fare.

Yes, if you buy a Blue Extra fare then SDC is included at no extra charge, however, that's not the case with Blue Plus so it's important to choose the correct fare if you're looking to avoid the fee as a non-Mosaic.

It will be interesting to see how B6 handles SDC for AA flights booked on Jetblue ticket stock.

AA's SDC policy is much more rigid- you have to keep original routing no changing of connecting airports where B6 SDC policy is in line with UA and other carriers your routing doesn't matter at all. So there might be a benefit of booking AA flights on B6 ticket stock if it is comparable price to buying AA flight on AA ticket stock when it comes to flexibility of SDC policy (even though Mosaics have complimentary SDC on AA issued tickets, I'm pretty sure AA agents will require keeping the original routing).

Been a Mosaic for over 6 years but didn't know they had a secret Mosaic text only line? I know Jetblue FB messenger is pretty quick to reply but I doubt they can handle Mosaic SDC requests. Can you share this text only Mosaic number?

Just sent it via PM.

Thanks! It is EXACTLY the same as the Mosaic elite calling number (the 1877 one) but I didn't realize that it also accepts texting as well. Good to know in the event of a 2+ hour callback wait.

Can I change a JFK-SJO to an earlier flight the same day to JFK-MCO-SJO?

I recall reading you can't do a SDC if there is only one direct flight a day.

You can't SDC in cities with only one flight a day. As mentioned earlier in this thread on page 1, if it's a routing that's for sale (which JFK-MCO-SJO is) and it's still available on the day of departure, you can SDC.

Can Mosaics get a SDC if the flight is booked with a travel certificate? Don't see a specific restriction on the certificate terms.

Yes. I've done it. Not as a Mosaic, but I've done it and paid the fee.

SDC if on a AA coded B6 flight?
 

If booked on a AA coded B6 flight, is a SDC possible?

From the website. I'm assuming you have to call this in.

1. Subject to availability. Mosaics, and eligible travelers on the same reservation, flying on American Airlines or American Eagle are eligible for free same-day flight changes beginning 24 hours before departure. Qualifying itineraries must depart on the same date, originate and terminate at the same airports, with the same intermediate airport stopovers, as original flight(s). TrueBlue number of Mosaic must be included in reservation record in advance of request. Travelers on the qualifying Mosaic reservations may not be split off or divided. All fare rules on date of change apply.

Has anyone ever successfully SDC'd a Jetblue operated booked with QR miles? I was told by a phone agent it has to be a flight earlier than the one booked (later ones not eligible) but wondering if anyone has actual experience.