I was just wondering about that myself. My parents will be moving down to live with me. Dad is on O2 and not entirely ambulatory.
We had considered air ambulance, but now I'm starting to think he might make it on an airline. We can drive 2 hrs to FNT, get him a seat in F/C, and NW has a direct flight to TPA. The route has very few elites, so I've almost always gotten upgrade. I will plan on getting an U/G. And I think we can either buy an upgrade for mom at the gate, or I can beg the flight attendant to let mom up front. I think if you don't want to pay for F/C, you can request & get the bulkhead row in coach.
NW said they have their own O2 we have to use, limited supply, must reserve 10 days in advance and there's a $100 charge. I think the wheelchairs will work out OK, but I'll have to call again.