I have traveled with a machine on plane many times since 9/11.
No matter what, I would NOT check it, even in original packing material. For some reason I think there's a liability limit on damaged/lost baggage, but beside that, I have seen handlers in the baggage claim area when turnstile (for lack of better word) wasn't working so they had to load up baggage manually, literally holding a box shipped w/baggage and letting loose of it so it dropped to the ground. And it was something breakable.... you heard it. I would absolutely ship ahead if not taking aboard.
That said, I've taken a Pfaff 7570 on board a couple times, made sure it fit in a wheel on suitcase (not sm case, regular suitcase like the flight attendants carry) that fit under the seat in front of me. On one carrier the seat was a bit lower and it didn't quite slide under... had my big coat draped over my legs so it was kind of hidden...

Even if they fit in the overhead compartment, I will not put them there, my personal choice. I don't want something that fragile falling either in an emergency or not nicely handled by others who don't care about anything but their own bag. If it fell somehow, it could not only damage the machine but cause great harm if it hit/fell on someone. Most likely someone with a personal injury lawyer on speed dial.
I have taken the smaller class size machine too, fit in a small tote (again I liked those from regular luggage section better than a sm specific model). Fit easily under seat in front. Have also taken it in original box.
I have also found that it is MUCH MUCH easier to get through security if BEFORE the machine gets to the xray "tunnel" you tell the security personnel checking the images that there's a sewing machine in there. THey're not used to seeing them (except at the Seattle airport around Puyallup show time!) and knowing ahead what's coming has (in my case) let it through no problem every time. Once the guy on other end said can you please open the bag. I did and he marvelled more at how machines had changed (that's why he wanted it opened, didn't look like old grandma's sm in the image!) but no problem. OTOH the one time I didn't, albeit soon after 9/11, they took it out of the box, out of styrofoam, wouldn't let me touch anything, swabbed it down....I know, I was profiled...
I always removed needles and put them in a checked bag.
I think contacting the airline is a good idea but to be honest sometimes they don't know how to answer this. At least you can get dimensions of under seat or overhead area. I would worry about weight these days. THey couldn't answer me about a certain size little thread trimmer scissor... so I took the guidelines printed out with me to airport to show that they fit the guidelines (they didn't know if they were ok but showed them and they let me through), could do same with sm. I haven't heard of any horror stories about an SM being refused anytime someone's asked. I did, long before 9/11, have Chicago O'Hare security tell me I couldn't take my sewing scissors on board (could see in bag I showed I had partly done Christmas stockings, materials, etc. in there with stocking partly sewn/hand appliqued. I said ok, I'll check them. I'll need a receipt to reclaim them on the way back. THey were pricey Ginghers! They didn't know how to handle that. Got a supervisor. Who didn't know what to do . The solution was to let me take them on board.

Four legs on that trip and no one either direction ever questioned it.