A cardboard box is luggage, right?

The movers came yesterday and sucked all my worldly goods out the front door. They showed up two hours early, just as I was pulling in the driveway with my freshly wormed cat, so I didn't get the orderly, premeditated move I was counting on.

So it's no surprise there was more stuff left out than I expected. I managed to cram it all into my trusty duffle, but then realized it probably exceeds the 50-pound weight limit. Is it okay if I take the excess and put it in a cardboard box? I'm flying Virgin out of Boston tonight and I can get the dimensions right...

My father-in-law has done this many times, and I've seen boxes going around the carousel. I think it's fine.

I would cover the whole box in packing tape to make sure it stays together.

It can't hurt to check with your airline, but I've seen people check in boxes before.  I had a huge triangular shaped cardboard box (my harp was inside--padded and bubblewrapped to high heaven!) and I checked that as a piece of excess luggage.  I don't think it was over the weight limit, just one piece extra. ( It only cost me $80 and made the journey safely and saved me hundreds of dollars if I had shipped it separately, by the way.)

We moved over with an ENORMOUS cardboard box as luggage. Definitely reinforce all the corners thoroughly with packing tape--ours arrived split down one corner. Nothing fell out, thankfully!

Boxes are fine.
Make sure it's nice and sturdy and make sure it is within the dimensions & weight guidelines unless you don't mind paying extra.  Most airlines will have that information on their homepage.
Also, I recommend there be a way for you to easily open them in case they want to inspect that box.  You'd never know.  And if they open it make sure there is a quick way for you to close the box and be on your merry way.

The box 'n' me made it through. I had to drop the cat at the freight place first, though. They told me there was a shuttle, so that was okay -- they didn't tell me the shuttle was, like, a tenth of a mile away. And it was raining.

Box 'n' me got thoroughly soaked. The top caved in completely. The man behind the ticket counter took one look and pulled a face. I whipped a roll of tape from my other bag and coccooned the box thoroughly and they let me check it.

So, yay! I wish I'd put more stuff in it now...

The box 'n' me made it through. I had to drop the cat at the freight place first, though. They told me there was a shuttle, so that was okay -- they didn't tell me the shuttle was, like, a tenth of a mile away. And it was raining.

Box 'n' me got thoroughly soaked. The top caved in completely. The man behind the ticket counter took one look and pulled a face. I whipped a roll of tape from my other bag and coccooned the box thoroughly and they let me check it.

So, yay! I wish I'd put more stuff in it now...

Glad you & your box made here it here safely.