okay.....so you're flying both ways on one airline.
you plan to reuse the box, so storage has been arranged.
now go to the airline website, find out what kind of aeroplane you'll be on.
( transatlantic flight, so cargo bays and doors shouldn't be a factor)
print off the baggage fees and regulations.
print off the policies for sporting equipment and oversized luggage.
carry these with you, along with the printout of any online chat
you have with an airline representative.
get the ezzact maximum dimensions permitted.
confirm those with the airline if possible.
hie thee to a home depot and secure a couple refrigerator boxes.
whilst there pick up a couple rolls of packing tape and a fresh box cutter.
now make your own dang box.
i usually fly the budget carriers between china and thighland and singapore.
always on A320's, with baggage dimensions such that i can usually stick a
nearly complete large-frame hybrid 700c into a box, along with helmet/shoes
and a stuffed pannier inside the triangle.
most i usually gots to do is remove the pedals and seat, ziptied onto the rear
rack, and then remove the stem and bars and ziptie to the top tube.
best of all, no tsa hoodlums, so bike always arrives unopened and undamaged.