I’m “with the passenger in a wheelchair” or perhaps “with the passenger who uses a wheelchair,” or most accurately, “with the hot guy using a wheelchair.”
But I guess this makes the distinction clear:
If you are a “wheel chair” or a stroller, you are not a “passenger.” You are your equipment.
And airline people, you don’t have “two wheelchairs on the plane.” As a matter of empirical fact, you have zero wheelchairs on the plane. You have two people who use wheelchairs who are waiting patiently on your plane for the doofuses (doofi?) in your ramp crew to figure out how to get their wheelchairs to the jetway.
I realize there are other circumstances in which an object associated with a person comes to stand for the person. “Suits” comes to mind, to mean the dweebs in the organization who are imposing rules on the real people who want to create/get things done/think outside the box. It’s not a compliment. “Brass” for officers, perhaps. “Uniforms” to distinguish beat cops from higher ranking detectives. I would put “wheelchair” as a substitute for the person in a very different category, though, largely because I only hear it from people in a position to treat the people themselves as objects.
I don’t take a position on the people-first language discussion, that is, whether it is better to say “disabled person” or “person with a disability.” Both seem better than “the disabled,” but as my disabled friend/friend with a disability Laura Hershey would say, English puts its adjectives before its nouns, so “disabled person” puts the focus on the person, it just does so grammatically.
But once you’ve taken the person out of the equation completely and substituted the thing, you’ve left the realm of grammar and made a decision to depersonalize.
The funny thing is, I always respond — when I hear this — “no I’m not with the wheelchair, I’m with the guy in the wheelchair” or to the airline peeps, “actually, you don’t have two wheelchairs on board, you have two people who use wheelchairs.” But no one even gets the difference.