Most likely the pet carrier would not even fit under a 1st class seat. What then?

Two reasons that this doesn't work. Currently DL does not allow any pets in the cargo holds. Many years ago they removed the option of traveling with pets as checked luggage and forced them to be transported as cargo. Since COVID there has been an embargo on accepting pets as cargo, except for military traveling on orders Shipping Pets (delta.com), so the only way to transport an animal on a DL flight is in cabin as a service animal or underseat in a carrier. Second, many underseat carriers are soft-side, made of fabric. For pet and airline personnel safety there are requirements for carriers placed in the cargo hold that they be hard sided, metal or strong plastic, and all openings secured so the animal cannot escape, usually ziptieing the door closed. Obviously, the in cabin carriers do not meet these safety requirements.

Usually when we reserve a spot on the plane (there are limits to how many in-cabin pets are allowed in each cabin) for our underseat dog, the reservation agent requests the carrier dimensions and checks a chart of allowed under seat sizes for each type of aircraft and for each cabin for those planes to see if the carrier will fit per DL's list of allowed carrier sizes. For soft sided carriers there is more wiggle room since the carrier can squash a a bit but hard sided carriers can't squash and can be an issue if space is tight. In this case someone messed up by allowing a passenger with an in-cabin pet book a bulkhead seat which obviously has no under seat room for a pet carrier. A big limit on underseat space turns out to be the electronics bay for the IFE since they are mounted under the seats.

what difference would it make if it were a non-rev

well that's just like, your opinion, man

people here act like just being ASKED to move is the worst possible thing that could ever happen to a human, give us a break. just say no. Nobody is "expecting" you in particular to change seats. Circumstances change, IROPs happen, people get rebooked, and sometimes people ask to change seats, you won't die from being asked, and if, god forbid, you actually are required to move for some reason, the good news is that the odds are extremely in your favor, I have yet to find any documented case of any human suffering irreprable harm from moving from one seat to another

I can say from experience that this was NOT na upgrade. If you have a pet in cabin and the only available seat is a bulkhead, they will go on to the next person on the list. They will not ask a paid FC pax to move for a complimentary upgrade.

Dogs always get divisive on FlyerTalk. We frequently fly with ours as a pet in cabin and follow the rules to a T— he goes in his bag before we check in and stays there quietly until we get outside of baggage claim.

I think we are in the majority but as a previous poster mentioned, policy isn’t what is written, it’s what’s enforced. A small handful of people do not follow the pet in cabin or service animal rules and have poorly behaved dogs of all shapes and sizes makes everyone’s travel experience worse. It’s very disrespectful and may someday cost us all the ability to travel with pets in cabin at all.

That is a very reasonable post.

Unfortunately most of us will notice and recall the few bad apples more than the good ones. Myself included,

I would probably never notice your dog. It is the jerks that I cannot stand. You know, the ones that do not follow the rules and think they are above everyone else.

Kid and I had 2 FC comp upgrades on a relatively short one hour flight. An ill elderly lady and her caregiver in MC were having a rough time so we voluntarily switched seats with them. It was no big deal. When we landed we got the red carpet treatment. Lead FA went out to the gate and got us set up with travel vouchers galore. And the pilot came out and gave us a huge thank you. Paid for the whole trip.

Why can't this happen more often?

Because they would have skipped over an upgrade from a long waitlist and then asked to move a cash customer to an inferior seat to accommodate them, rather than just seating them in coach where the dog carrier wouldn't have been an issue?

thanks. I was not aware of those constraints. I know my attitude is unpopular, but become a “no pets, just service animals” airline then?

While this is an option there are many people who find themselves in situations where flying with a pet is the most practical option. Moving cross country where driving takes too long or is expensive. Transporting an animal to a new owner, transporting a performance/show animal to a competition, transporting an animal to a training center, etc. Pre-COVID this would have to be by cargo with larger animals but that is difficult now. Transporting an animal as cargo opens a new set of issues, if you miss a connection you can cope, is stuff misses a connection, no big deal, if an animal misses a connection someone has to feed it, give it water, let it out to relieve itself, etc. If your bags get misrouted, they will be OK until you get them back several days later. What about a dog or cat locked in a crate for several days? For 2016 there were at least 26 animal deaths reported by airlines and as many injuries, so shipping animals by cargo does entail real risks to the animal. So while banning animals from airlines may make many passengers more comfortable it removes a valuable service to those individuals who have to move animals long distance.

Here's a thought, leave your pets at home!

Easier said than done. You’ve obviously never had to have moved 4000 miles with a dog where driving was not an option.